# geocat.comp.meteorology.heat_index#

geocat.comp.meteorology.heat_index(temperature, relative_humidity, alternate_coeffs=False)#

Compute the ‘heat index’ as calculated by the National Weather Service.

The heat index calculation in this funtion is described at: https://www.wpc.ncep.noaa.gov/html/heatindex_equation.shtml

The ‘Heat Index’ is a measure of how hot weather “feels” to the body. The combination of temperature and humidity produce an “apparent temperature” or the temperature the body “feels”. The returned values are for shady locations only. Exposure to full sunshine can increase heat index values by up to 15°F. Also, strong winds, particularly with very hot, dry air, can be extremely hazardous as the wind adds heat to the body

The computation of the heat index is a refinement of a result obtained by multiple regression analysis carried out by Lans P. Rothfusz and described in a 1990 National Weather Service (NWS) Technical Attachment (SR 90-23). All values less that 40F/4.4C/277.65K are set to the ambient temperature.

In practice, the Steadman formula is computed first and the result averaged with the temperature. If this heat index value is 80 degrees F or higher, the full regression equation along with any adjustment as described above is applied. If the ambient temperature is less the 40F (4.4C/277.65K), the heat index is set to the ambient temperature.

Parameters:
Returns:

heatindex (`numpy.ndarray`, `xarray.DataArray`) – Calculated heat index. Same shape as `temperature`

Examples

```>>> import numpy as np
>>> import geocat.comp
>>> t = np.array([104, 100, 92])
>>> rh = np.array([55, 65, 60])
>>> hi = heat_index(t,rh)
>>> hi
array([137.36135724, 135.8679973 , 104.68441864])
```

Related GeoCAT Functions: `_heat_index()` `_xheat_index()`