Our latest innovation is the addition of our own global heat index, humidex and apparent temperature to our Weather API. Helping organizations better understand and mitigate the impacts of heat.

Meteomatics Heat Index and Humidex are available from 1.1.1979 and up to 45 days forecast (including the ecmwf-vareps forecast)

Meteomatics Heat Index (heat stress 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. For example, if the air temperature is 36 °C with a relative humidity of 60 %, the heat index is 47 °C.

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.

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 The computation of this index requires air temperatures and dew point temperatures.

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

Apparent Temperature (feels like 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.

Since the Heat Index is defined for shaded areas, the apparent temperature can be several degrees higher due to the effect of global radiation.  

Apparent temperature and air temperature at a height of 2 meters over five days

Website: www.meteomatics.com 

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