Derived Weather Parameters - Temperature Related Parameters

Windchill | Apparent Temperature | Heat Index | Humidex | Wet-bulb Temperature | Equivalent Potential Temperature | Lake Temperatures | Mean temperature of last 10 years


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



Apparent Temperature

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.


Available units: C, F, K Examples

Heat Index

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

Heat Index Description
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
>54 °C Extreme danger: heat stroke is imminent



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

Heat Index Description
20 - 29 °C Little to no discomfort
30 - 39 °C Some discomfort
40 - 45 °C Great discomfort; avoid exertion
>45 °C Dangerous, heat stroke possible


Wet-bulb Temperature

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.


Available levels: 0m, 2m, 100m, 1000hPa, 975hPa, 950hPa, 925hPa, 900hPa, 875hPa, 850hPa, 825hPa, 800hPa, 775hPa, 750hPa, 700hPa, 650hPa, 600hPa, 550hPa, 500hPa, 450hPa, 400hPa, 350hPa, 300hPa Examples

Equivalent Potential Temperature (θe)

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.


Available levels: 2m - 20000m (continuously), 1000hPa, 975hPa, 950hPa, 925hPa, 900hPa, 875hPa, 850hPa, 825hPa, 800hPa, 775hPa, 750hPa, 700hPa, 650hPa, 600hPa, 550hPa, 500hPa, 450hPa, 400hPa, 350hPa, 300hPa, 200hPa, 50hPa, 10hPa

Available units: C, K


Lake Temperatures

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:


In order to perform a query for a certain lake, the coordinates are required as input. A list of all available lakes can be fetched by applying a find station query (see Find Station). For example, the following query creates a list of all available lakes within Germany: The query for the lake temperature must contain the coordinates, the lake temperature parameter t_lake:C and the lake model specification mm-lake-temp:

This example shows the lake temperature for Lake Constance. Current lake temperature with 15-day forecast for Lake Constance:,9.37955/html?source=mm-lake-temp&on_invalid=fill_with_invalid

Mean Temperature over the Last 10 Years

The mean 2m-temperature over the last 10 years on a certain date at a specific location.


Available units: K, C Examples