Derived Weather Parameters

This is an overview of all derived weather parameters and convenience Parameters. Below, each parameter is explained in more detail.

Weather Symbol | Weather Code | Visibility | Dew or Rime | Rainfall | Sleet | Snowfall | Fog | Frost Warning | Windchill | Icing Potential | Slippery Road | Power Line Oscillation Warning | Bise Index | Foehn Index | Moehlin Jet Index | Santa Ana Wind Index | North Atlantic Oscillation Index | Southern Oscillation Index | Forest Fire Index by Kaese | Fosberg Fire Weather Index | Drought Index | Stratospheric Polar Vortex

General Weather State

Weather symbol

The weather symbol is the easiest way to query an overview of the weather state.

weather_symbol_1h:idx

Examples

• Show the weather symbols for the next 5 days. A table with the different symbols and their meaning can be viewed below.
  https://api.meteomatics.com/today_replaceT00:00:00ZP5D:PT1H/weather_symbol_1h:idx/50,10/html
  

  

Symbol Id (Day)	Symbol Id (Night)	Description
0	0	A weather code could not be determined
1	101	Clear sky
2	102	Light clouds
3	103	Partly cloudy
4	104	Cloudy
5	105	Rain
6	106	Rain and snow / sleet
7	107	Snow
8	108	Rain shower
9	109	Snow shower
10	110	Sleet shower
11	111	Light Fog
12	112	Dense fog
13	113	Freezing rain
14	114	Thunderstorms
15	115	Drizzle
16	116	Sandstorm

Weather Code

Weather code according to the present weather code 4677 of the international WMO Standard² (mean for 1h, 3h, 6h, 12h, 24h)

weather_code_<interval>:idx

Weather symbol mean for 1h, 3h, 6h, 12h, 24h

Examples

• Show the weather codes for the next five days.https://api.meteomatics.com/today_replaceT00:00:00ZP5D:PT1H/weather_code_1h:idx/47.412164,9.340652/html

  

  The weather codes in this plot are:00 - Cloud development not observed or not observable49 - Fog, depositing rime, sky invisible70 - Intermittent fall of snowflakes, slight at time of ob.

  71 - Continuous fall of snowflakes, slight at time of ob.

  73 - Continuous fall of snowflakes, moderate at time of ob.

  77 - Snow grains (with or without fog)

Weather Text

This parameter provides an automated text snipped describing the general weather state of the queried day. It is currently available in English, German, French and Italian.

weather_text_de:str
weather_text_en:str
weather_text_fr:str
weather_text_it:str

Example

• Show the weather text for today: https://api.meteomatics.com/today_replaceT00:00:00Z/weather_text_en:str/50,10/csv

validdate;weather_text_en:str
2019-04-08T00:00:00Z;Today after sunrise the sky will be overcast.
In the afternoon it will be mostly sunny. About 4 hours of sunshine are predicted. 
It stays very balmy with temperatures between 9°C and 16°C. 
After daybreak there is a slight northeasterly wind which shifts afterwards to a slight southerly wind. 
In the late evening the sky is partly cloudy, in the second half of the night dense mist may appear. 

Visibility

This parameter returns the visibility in kilometers. You can expect foggy conditions if the visibility is less than about 1km.

visibility:km

Examples

• Show the predicted evolution of the visibility for five days.https://api.meteomatics.com/2017-02-07T00:00:00ZP5D:PT1H/visibility:km/47.412164,9.340652/html

  

• To obtain the data in a different output format, just replace the format parameter in the URL with one of the following: csv, json, xml, png, html, netcdf, grads.
  Here is an example for the xml format:   

   

  https://api.meteomatics.com/today_replaceT00:00:00ZP1D:PT3H/visibility:km/47.412164,9.340652/xml

  

Dew or Rime

This index gives you an idea whether dew or rime will occur. Dew or rime forms if the surface cools down quicker than the surrounding air, which causes condensation onto the surface at high relative humidities. Dew and rime are very sensitive to solar radiation and disappear quickly as the surface warms. Rime is the frozen version of dew.

0: neither dew nor rime, 1: dew, -1: rime

dew_or_rime:idx

Example

• Dew or rime forecast for the next two days along with the expected temperatures. On the 8th March, 2017, some dew was expected from 3 to 5 a.m. This was expected to be followed by some rime one hour later, when the temperature dropped significantly.https://api.meteomatics.com/2017-03-07T00:00:00ZP2D:PT1H/dew_or_rime:idx,t_0m:C/47.412164,9.340652/html

  

Rainfall

Check if there was any rain within the last 30 minutes or last hour.

0: no rain, 1: rain event

is_rain_<interval>:idx

Available intervals: 30min, 1h

Examples

• Show if there is rain in the next two days along with the temperature and expected amount of precipitation within 30 minutes.https://api.meteomatics.com/2017-03-08T00:00:00ZP2D:PT30M/is_rain_30min:idx,t_2m:C,precip_30min:mm/47.412164,9.340652/html

  

• A part of the corresponding csv file.https://api.meteomatics.com/today_replaceT00:00:00ZP2D:PT30M/is_rain_30min:idx,t_2m:C,precip_30min:mm/47.412164,9.340652/csv

  validdate;is_rain_30min:idx;t_2m:C;precip_30min:mm
  2017-03-08T12:00:00Z;0;8.3;0.02
  2017-03-08T12:30:00Z;1;8.3;0.04
  2017-03-08T13:00:00Z;0;8.3;0.02
  2017-03-08T13:30:00Z;1;8.2;0.21
  2017-03-08T14:00:00Z;1;8.2;0.23
  2017-03-08T14:30:00Z;1;6.7;0.42
  2017-03-08T15:00:00Z;1;5.3;0.64
  2017-03-08T15:30:00Z;1;4.8;0.6
  2017-03-08T16:00:00Z;1;4.3;0.88
  2017-03-08T16:30:00Z;1;4.9;0.56

Sleet

Check if there was any sleet within the last hour or last 30 minutes.

0: no sleet, 1: sleet event

is_sleet_<interval>:idx

Available intervals: 30min, 1h

Example

• Show if there is any sleet expected during the next four days. The expected temperature and precipitation are also shown on the same plot as these parameters depend on each other.https://api.meteomatics.com/2017-02-05T00:00:00ZP4D:PT1H/is_sleet_1h:idx,t_2m:C,precip_1h:mm/47.412164,9.340652/html

  

Snowfall

Check if there was any snowfall within the last hour or last 30 minutes.

0: no snowfall, 1: snowfall event

is_snow_<interval>:idx

Available intervals: 30min, 1h

Example

• Show if there is any snow expected in the next four days. The temperature and precipitation are also shown for this period as the snow event depends on them.https://api.meteomatics.com/2017-01-02T00:00:00ZP4D:PT1H/is_snow_1h:idx,t_2m:C,precip_1h:mm/47.412164,9.340652/html

  

Fog

Check if there was any fog within the last hour or 30 minutes.

0: no fog, 1: fog event

is_fog_<interval>:idx

Available intervals: 30min, 1h

Example

• Show if there is any fog expected during the next four days. The visibility is also shown as the two parameters contain similar information.https://api.meteomatics.com/today_replaceT00:00:00ZP5D:PT1H/visibility:km,is_fog_1h:idx/47.412164,9.340652/html

  

• Another example as a json output for fog expectation during the next six hours.https://api.meteomatics.com/today_replaceT00:00:00ZPT6H:PT1H/visibility:km,is_fog_1h:idx/47.412164,9.340652/json

  {"version":"3.0","user":"api-test","dateGenerated":"2018-02-07T16:10:49Z","status":"OK","data":
  [{"parameter":"visibility:km","coordinates":[{"lat":47.4122,"lon":9.34065,"dates":
  [{"date":"2017-02-07T00:00:00Z","value":20},{"date":"2017-02-07T01:00:00Z","value":20},
  {"date":"2017-02-07T02:00:00Z","value":20},{"date":"2017-02-07T03:00:00Z","value":20},
  {"date":"2017-02-07T04:00:00Z","value":20},{"date":"2017-02-07T05:00:00Z","value":20},
  {"date":"2017-02-07T06:00:00Z","value":20}]}]},
  {"parameter":"is_fog_1h:idx","coordinates":[{"lat":47.4122,"lon":9.34065,"dates":
  [{"date":"2017-02-07T00:00:00Z","value":0},{"date":"2017-02-07T01:00:00Z","value":0},
  {"date":"2017-02-07T02:00:00Z","value":0},{"date":"2017-02-07T03:00:00Z","value":0},
  {"date":"2017-02-07T04:00:00Z","value":0},{"date":"2017-02-07T05:00:00Z","value":0},
  {"date":"2017-02-07T06:00:00Z","value":0}]}]}]}

Frost

The parameter indicates if there is any frost.

0: no frost, 1: frost is likely, 2: frost

frost_warning:idx

Examples

• Show the surface temperature along with the frost warning index for the next five days.https://api.meteomatics.com/today_replaceT00:00:00ZP5D:PT1H/frost_warning:idx,t_0m:C/47.412164,9.340652/html

  

Windchill

Gives the wind chill in °C as defined by Wikipedia¹ .

windchill:C

Examples

• Show the windchill and the temperature at a height of 2 meters for the next five days.https://api.meteomatics.com/today_replaceT00:00:00ZP5D:PT1H/windchill:C,t_2m:C/47.412164,9.340652/html

  

Icing Potential

Icing is absolutely critical in aviation and in-flight icing on planes are the cause of multiple near-accidents or even crashes. Consequently, it is crucial for aviation to have reliable icing forecasts predicting the expected occurrence of icing on different altitudes and allowing for early circumnavigation.

icing_potential_<level>:idx

Available levels: 1000hPa,950hPa,925hPa,900hPa,850hPa,800hPa,700hPa,500hPa,300hPa

Index	Description
0.0-0.2	No Icing
0.2-0.4	Traces
0.4-0.6	Light
0.6-0.8	Moderate
0.8-1.0	Heavy

Examples

• Below showing an example screenshot of the icing potential at 500hPa displayed via the powerful Meteomatics WMS interface. Very well visible the icing potential along the cold front associated with the strong low pressure system West of Ireland.
  
• Hourly icing forecast on several layers for the next 5 days in one location:
  http://api.meteomatics.com/today_replaceT12ZP5D:PT1H/icing_potential_300hPa:idx,icing_potential_500hPa:idx,icing_potential_800hPa:idx/47.457625,8.555272/html
  

Slippery Road

Check if there is any chance for slippery roads within the given interval.

0: no slippery road conditions, 1: slippery roads possible

is_slippery_road_<interval>:idx

Available intervals: 1h, 3h, 6h, 12h, 24h

Examples

• check if slippery roads are possible in the next five days.https://api.meteomatics.com/2017-01-02T00:00:00ZP1D:PT1H/is_slippery_road_1h:idx/47.412164,9.340652/html

  

• The possibility of slippery roads in the next five days in 12 hours steps as a json file output.https://api.meteomatics.com/today_replaceT00:00:00ZP5D:PT12H/is_slippery_road_12h:idx/47.412164,9.340652/json

  {"version":"3.0","user":"api-test","dateGenerated":"2018-02-07T16:17:17Z","status":"OK","data":
  [{"parameter":"is_slippery_road_12h:idx","coordinates":[{"lat":47.4122,"lon":9.34065,"dates":
  [{"date":"2017-01-01T00:00:00Z","value":0},{"date":"2017-01-01T12:00:00Z","value":0},
  {"date":"2017-01-02T00:00:00Z","value":0},{"date":"2017-01-02T12:00:00Z","value":0},
  {"date":"2017-01-03T00:00:00Z","value":0},{"date":"2017-01-03T12:00:00Z","value":0},
  {"date":"2017-01-04T00:00:00Z","value":0},{"date":"2017-01-04T12:00:00Z","value":1},
  {"date":"2017-01-05T00:00:00Z","value":1},{"date":"2017-01-05T12:00:00Z","value":1},
  {"date":"2017-01-06T00:00:00Z","value":0}]}]}]}

Power line oscillation warning

Precipitation in the form of freezing rain or wet snow can freeze onto overland power lines. With the increase in diameter and mass come a bigger air resistance and a lower resonance frequency. Strong wind over a sufficient amount of time could then excite the conductors to oscillate near their resonance frequency (sometimes referred to as gallop) and thereby damage the lines and masts.

A power line oscillation warning for the past 24 hours can be queried with the following parameter:

power_line_oscillation_24h:idx

The warning is binary with 1 corresponding to a warning and 0 to an all clear. Not taken into account are things like constructional details of the power lines or the Joule heat emitted by active power lines.

Example

• On March 24 2016, there was a power outage in Halton Hills due to galloping power lines, which is exemplified by the following time series:https://api.meteomatics.com/2016-03-24T00:00:00ZPT18H:PT1H/power_line_oscillation_24h:idx/43.64,-79.931944/html

  

Wind phenomena

Bise Index

This parameter computes an index to determine whether there is a bise or not and its strength. The bise is usually a cold wind from North-Easterly directions in the Lake Constance area which affects local weather conditions, including those of the Swiss Plateau. It is mainly triggered by a large scale air pressure difference between a low in the South-West of the Alps and a high on the northern side of the Alps. As a rule of thumb, if the pressure difference between Geneva and Constance is less that -2 hPa, bise conditions are expected.

bise_index:hPa

Example

• The chart below explains how to interpret a time series of the bise indexhttps://api.meteomatics.com/2017-03-08T00:00:00ZP5D:PT1H/bise_index:hPa/47.412164,9.340652/html

  

Foehn Index

This parameter computes an index to determine the presence, strength, and direction of the Alpine Foehn. The Foehn is usually a strong, warm, dry wind crossing the Alps from the South-East to the North, but can also move in the the opposite direction. It mainly affects alpine valleys. Usually, it is triggered by large scale air pressure differences between a high in the South of the Alps and a low in the North-West of the Alps. As a rule of thumb, if the pressure difference between Lugano and Zurich is higher than 4 hPa, Foehn conditions are expected in the northern part of the Alps. If the pressure difference is less than -4 hPa, Foehn conditions are ecpected in the southern part of the Alps.

foehn_index:hPa

Example

• The time series shown below demonstrates an example of Foehn conditions in the Swiss Alpshttps://api.meteomatics.com/2017-05-08T00:00:00ZP5D:PT1H/foehn_index:hPa/47.412164,9.340652/html

  

• Another example of Foehn conditions in the Swiss Alps as a json file. The positive numbers are South Foehn and the negative North Foehn.https://api.meteomatics.com/2018-01-01T00:00:00ZP2D:PT6H/foehn_index:hPa/47.412164,9.340652/json

  {"version":"3.0","user":"api-test","dateGenerated":"2018-02-14T13:13:58Z","status":"OK","data":
  [{"parameter":"foehn_index:hPa","coordinates":[{"lat":47.4122,"lon":9.34065,"dates":
  [{"date":"2018-01-01T00:00:00Z","value":6.4},{"date":"2018-01-01T06:00:00Z","value":-1.4},
  {"date":"2018-01-01T12:00:00Z","value":0.4},{"date":"2018-01-01T18:00:00Z","value":4.3},
  {"date":"2018-01-02T00:00:00Z","value":-3.9},{"date":"2018-01-02T06:00:00Z","value":-3.6},
  {"date":"2018-01-02T12:00:00Z","value":-3.4},{"date":"2018-01-02T18:00:00Z","value":-1.9},
  {"date":"2018-01-03T00:00:00Z","value":3.7}]}]}]}

Moehlin Jet Index

The Moehlin Jet is a south-easterly wind that originates from the Frick Valley and is responsible for dissolving fog in the region of Basel. This is the reason why sunshine duration there clearly exceeds the one of the Swiss midlands in fall. Favoring conditions are winterly high pressure situations over Switzerland, when the midlands act as a cold air pool. If the pool is full, the cold air masses spill over and follow gravity towards Moehlin, while the air is dried and heated on the way. The index takes values of 0 and 1, where 1 indicates the presence of a Moehlin Jet.

moehlin_jet:idx

Example

• On December 5 2016 there was a particularly lasting Moehlin Jet as indicated by the time series below:https://api.meteomatics.com/2016-12-03T00:00:00ZP4D:PT2H/moehlin_jet:idx/47.559,7.844/html

  

Santa Ana Wind Index

This parameter computes the presence and strength of the Santa Ana Winds in southern California. These are strong and extremely dry down-slope winds that originate from the desert and descend towards coastal areas. They develop if dry, cool high-pressure air masses are prevailing in the Great Basin and low pressure over the Pacific. Typically, these events occur in fall. Due to the extremely low relative humidities, such an event provides eligible conditions for wildfires. The index takes values in the range of 0 to 1. If the index exceeds 0.6, Santa Ana Winds can be expected.

santa_ana_wind:idx

Example

• The following time series indicates the strong Santa Ana Winds that fueled the California wildfires during December 2017:https://api.meteomatics.com/2017-12-02T00:00:00ZP15D:PT3H/santa_ana_wind:idx/34,-118.5/html

  

• A part of the corresponding csv file:https://api.meteomatics.com/2017-12-02T00:00:00ZP15D:PT3H/santa_ana_wind:idx/34,-118.5/csv

  validdate;santa_ana_wind:idx
  2017-12-05T21:00:00Z;0.8
  2017-12-06T00:00:00Z;0.6
  2017-12-06T03:00:00Z;0.6
  2017-12-06T06:00:00Z;0.5
  2017-12-06T09:00:00Z;0.7
  2017-12-06T12:00:00Z;0.8
  2017-12-06T15:00:00Z;0.8
  2017-12-06T18:00:00Z;0.7
  2017-12-06T21:00:00Z;0.7
  2017-12-07T00:00:00Z;0.6

North Atlantic Oscillation Index

The North Atlantic Oscillation describes pressure fluctuations between the Icelandic low and the Azores high. This parameter is computed with the sea level pressures of Ponta Delgada on the Azores Islands and Reykjavík. A positive NAOI implies that increased westerlies are present, which result in cool and contrary weather conditions. If the NAOI is negative, then the westerlies are suppressed and blocking situations can occur, which are responsible for stable weather conditions. The index changes daily.

north_atlantic_oscillation:idx

Example

• Below the time series of the index for the year 2017:https://api.meteomatics.com/2017-01-01T00:00:00ZP1Y:P1D/north_atlantic_oscillation:idx/64.14,-21.86/html

  

• Following you can see the json output for ten days in August:https://api.meteomatics.com/2017-08-01T00:00:00ZP10D:P1D/north_atlantic_oscillation:idx/64.14,-21.86/json

  {"version":"3.0","user":"api-test","dateGenerated":"2018-02-28T08:09:07Z","status":"OK","data":
  [{"parameter":"north_atlantic_oscillation:idx","coordinates":[{"lat":64.14,"lon":-21.86,"dates":
  [{"date":"2017-08-01T00:00:00Z","value":0.3},{"date":"2017-08-02T00:00:00Z","value":0.2},
  {"date":"2017-08-03T00:00:00Z","value":0.6},{"date":"2017-08-04T00:00:00Z","value":1.2},
  {"date":"2017-08-05T00:00:00Z","value":1.5},{"date":"2017-08-06T00:00:00Z","value":1},
  {"date":"2017-08-07T00:00:00Z","value":0.9},{"date":"2017-08-08T00:00:00Z","value":0.9},
  {"date":"2017-08-09T00:00:00Z","value":1.1},{"date":"2017-08-10T00:00:00Z","value":1.4},
  {"date":"2017-08-11T00:00:00Z","value":1.6}]}]}]}

Southern Oscillation Index

The Southern Oscillation is the atmospheric contributor to El Niño. The oscillation describes a reversal of surface pressure over Indonesia and the eastern Pacific. This index is used as an indicator for the strength of the southern oscillation and to assess the relative strength of the trade winds. If the Index is positive, the pressure over Indonesia is higher than over the eastern Pacific. This situation is referred to as El Niño. If the index is negative, the pressure over the eastern Pacific is higher. This situation is then referred to as La Niña. If the index is equal to zero, then neutral conditions are prevailing. The index changes daily.

southern_oscillation:idx

Example

• The strong El Niño phase during the years 2015 and 2016 is shown in the time series below:https://api.meteomatics.com/2014-06-01T00:00:00ZP3Y:P5D/southern_oscillation:idx/0,117/html

  

Forest Fire Risk Indices

Forest Fire Index by Käse

The Forest Fire Index according to Käse estimates the risk of forest fire on a daily basis. Each day's index is calculated using that from the previous day. It is only computed for days 46-274 of the year. Outside this range it is 0. The scale ranges from 1 to 5. A value of 1 indicates low risk, while a value of 5 indicates very high risk.

forest_fire_index_kaese:idx

Examples

• Show the forest fire index over a period of 60 days along with the daily precipitation sum. It is clear to see that the fire index is low if there is rain and high if it has been dry for several days.https://api.meteomatics.com/2017-03-01T00:00:00ZP60D:PT24H/forest_fire_index_kaese:idx,precip_24h:mm/47.412164,9.340652/html

  

• The forest fire index without the precipitation. The data are shown as a csv format over a few days in August.https://api.meteomatics.com/2017-08-01T00:00:00ZP10D:PT24H/forest_fire_index_kaese:idx/47.412164,9.340652/csv

  validdate;forest_fire_index_kaese:idx
  2017-08-01T00:00:00Z;1
  2017-08-02T00:00:00Z;1
  2017-08-03T00:00:00Z;1
  2017-08-04T00:00:00Z;2
  2017-08-05T00:00:00Z;2
  2017-08-06T00:00:00Z;1
  2017-08-07T00:00:00Z;1
  2017-08-08T00:00:00Z;1
  2017-08-09T00:00:00Z;0
  2017-08-10T00:00:00Z;0
  2017-08-11T00:00:00Z;0

Fosberg Fire Weather Index

The Fosberg fire weather index indicates the risk for bush/grass fire and ranges from 0 to 100 (continuous scale). The fire danger is evaluated according to the present weather without taking into account past weather conditions.

fosberg_fire_weather_index:idx

Examples

• Show the Fosberg Index along with the daily precipitation sum.https://api.meteomatics.com/2017-04-23T00:00:00ZP10D:PT24H/fosberg_fire_weather_index:idx,precip_24h:mm/47.412164,9.340652/html

  

Drought Index

This index forecasts whether a certain location is under a drought or not. The percentiles of the deviation of the current time window from the mean of the past years is computed. The percentiles are then grouped into bins which gives the following output scale for the drought index:

Percentile	0-10	10-20	20-30	30-40	40-60	60-70	70-80	80-90	90-100
Index	-4	-3	-2	-1	0	1	2	3	4

drought_index:idx

Examples

• Create a time series for a period of 35 days.https://api.meteomatics.com/2017-06-10T00:00:00Z/drought_index:idx/47.412164,9.340652/html

  

Stratospheric Polar Vortex (SPV): Wind speed

This index provides the average wind speed at 10, 50 or 200 hPa between 60°N and 90°N and thus indicates the strength of the stratospheric polar vortex during the polar winter.
The SPV index provides a measure of the circumpolar vortex strength and indirectly relates to a risk of cooling temperatures near the surface in the northern hemisphere, if decreasing below zero.
If the index becomes negative, the vortex disruption is such that a “split" or strong “displacement" is under way, possibly weakening the jet stream in the troposphere.

Example

• Show the historical and forecast SPV strength at 10, 50 and 200 hPa:http://api.meteomatics.com/2018-11-01T00ZP100D:P1D/polar_vortex_10hPa:ms,polar_vortex_50hPa:ms,polar_vortex_200hPa:ms/50,10/html

  

1. Wikipedia Page of Wind Chill: https://en.wikipedia.org/wiki/Wind_chill
2. WMO Weather Code Standard: https://badc.nerc.ac.uk/data/surface/code.html