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.
This parameter returns the visibility in kilometers. You can expect foggy conditions if the visibility is less than about 1km.
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:
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 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:
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.
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.
The planetary boundary layer (PBL) height is determined by identifying the height, where big wind direction changes, local minima of wind speed, local maxima of temperature, high temperature increases (inversion) or high potential temperature increases occur.
The freezing level parameter provides the altitude where the temperature equals 0 °C. If the freezing level is below ground, the return value is -666. In case of strong convection, the height of the freezing level correlates with the size of hail observed at the surface, since it determines the melting area for falling hail.
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.
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:
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.
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:
The leisure index combines different weather parameters and assesses if weather conditions are favorable for certain outdoor activities or not. The index ranges from 0 to 1, where 1 means that conditions are perfect for the queried activity at the queried point in time (i.e. the parameter is instantaneous).
The indices are based on a combination of precipitation, temperature, wind speed, wind gusts, humidity, sunshine duration, snow cover, visibility and fog.
Available activities: ballooning, bbq, beach, biking, climbing, fishing, gardening, gliding, hiking, hunting, sailing, skiing, tv
This index combines several weather parameters like temperature, wind speed, humidity and precipitation and assesses how favorable these weather conditions are for catching a cold. The index takes values from 1 to 100, where higher values indicate higher risks.
Time series showing the cold index for St. Gallen on the 17th of January, 2020:
The apparent temperature is a measure for the human thermal comfort. On the basis of the air temperature, the apparent temperature is computed considering effects of relative humidity, wind speed and solar radiation.
The Heat Index is a parameter that describes how humidity affects the perception of warm temperatures in shaded areas. Since the human body cools itself by evaporating sweat from the skin, higher humidity attenuates the effect of this mechanism. The index is computed using air temperature and relative humidity, while for temperatures below 27°C the heat index equals air temperature. The Heat Index can be used to assess the danger of heat exhaustion and strokes when performing outdoor activities.
Available units: C, F, K
26 - 32 °C
Caution: fatigue is possible, activity could result in heat cramps
32 - 41 °C
Extreme caution: heat cramps and heat exhaustion possible, activity could result in heat stroke
41 - 54 °C
Danger: heat cramps and heat exhaustion are likely, heat stroke is probable
Extreme danger: heat stroke is imminent
Heat Index and temperature for Miami in September. 2019:
The Humidex is the Canadian equivalent of the Heat Index. It also describes the effects of humidity in combination with high temperatures. The computation of this index requires air temperatures and dew point temperatures.
Available units: C, F, K
20 - 29 °C
Little to no discomfort
30 - 39 °C
40 - 45 °C
Great discomfort; avoid exertion
Dangerous, heat stroke possible
Humidex and temperature for Miami in September. 2019:
The wet-bulb temperature is the lowest temperature that can be reached by direct evaporative cooling. Thereby, the release of water from a saturated surface and the water absorption capacity of the surrounding atmosphere are in equilibrium. Due to the cooling by evaporation, the wet-bulb temperature always falls below the air temperature in dependence of the relative humidity. The difference between wet-bulb temperature and air temperature is larger if the air is drier. The wet-bulb temperature exceeds the dew point temperature, except for relative humidities of 100 %, where air temperature, wet-bulb temperature and dew point temperature coincide.
θe is a conserved quantity during vertical motions in the atmosphere. It is the temperature an air parcel would reach if all the water vapor condensed and its latent heat was released, while the parcel is lifted adiabatically to 1000 hPa.
The concept of θe is a powerful tool in order to differentiate between different air masses, which facilitates the identification of frontal systems. Moreover, it allows the assessment of atmospheric stability. If θe decreases with height, the atmosphere is unstable and convection is favored.
Meteomatics launched its own model for computing lake temperatures. The temperatures are calculated for a vast amount of lakes within Germany, Switzerland and Austria. Historical data is available back to 2015 and a 15-day forecast is provided daily. The resolution of the temperature data is 1 hour.
The model can be accessed via:
The corresponding lake temperature parameter has the following identification within the API:
This parameter computes an index to determine whether there is a bise 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 and the wind direction is North-East, then bise conditions are expected. If all conditions are met the value of the index is 1 and Bise is expected, otherwise the index is 0.
Bise conditions in Sankt Gallen, on October 28th, 2019:
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, and the wind direction is South-East to the NorthFoehn, or vice versa, then foehn conditions are expected in the southern part of the Alps.
If all conditions are met for North Foehn winds to be expected, the value of the index is 1, otherwise it is 0.
North Foehn conditions in Verona, on December 21st, 2019:
The Moehlin Jet is a south-easterly local 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.
On December 4th and 5th, 2016 there was a particularly lasting Moehlin Jet as indicated by the time series below:
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.
The following time series indicates the strong Santa Ana Winds that fueled the California wildfires during December 2017:
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.
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.
The strong El Niño phase during the years 2015 and 2016 is shown in the time series below:
The Forest Fire Index estimates the risk of forest fires based on moisture information of three different soil layers. The index ranges from 0 to 1, where the risk increases for values exceeding 0.5. A value of 0 indicates low risk, while a value of 1 indicates very high risk.
The forest fire index for a period during spring/summer in 2018 for St. Gallen:
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.
Show the Fosberg Index along with the daily precipitation sum in spring 2017:
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:
The soil moisture index indicates the wetness of the soil. This index is computed using the permanent wilting point and the field capacity, which both depend on the geographical location (soil type). The index is 0 if the permanent wilting point is reached and 1 at field capacity. Note that the index can exceed 1 after rainfall events. The soil moisture index is available for 4 depth levels.
This parameter computes the difference between the actual water content of the soil and the possible water content that the soil can hold in mm. The amount of water that can be hold is called field capacity. The calculation of the SMD is mainly based on soil water information in several depths as well as other meteorological parameters. The SMD is a useful tool in order to assess prevailing soil conditions like droughts. The SMD also depends on the soil type.
Course of the SMD during 2019 in the south-east in the UK: