varunayan.heat_stress module¶

Heat stress index calculations.

Calculate relative humidity from temperature and dewpoint using Magnus-Tetens formula.

Parameters:

temp_c – Air temperature in Celsius
dewpoint_c – Dewpoint temperature in Celsius

Returns:

Relative humidity as percentage (0-100)

varunayan.heat_stress.vapor_pressure_from_dewpoint(dewpoint_c: float | ndarray | Series) → float | ndarray | Series[source]¶

Calculate vapor pressure from dewpoint using Magnus formula.

Parameters:: dewpoint_c – Dewpoint temperature in Celsius
Returns:: Vapor pressure in hPa

Reference: Bolton (1980), Mon. Wea. Rev. 108, 1046-1053.

Calculate wet bulb temperature using Stull (2011) empirical formula.

Reference: Stull, R. (2011). Wet-Bulb Temperature from Relative Humidity and Air Temperature. J. Appl. Meteor. Climatol., 50, 2267-2269.

Parameters:

temp_c – Air temperature in Celsius
rh – Relative humidity as percentage (0-100)

Returns:

Wet bulb temperature in Celsius

varunayan.heat_stress.wet_bulb_from_dewpoint(temp_c: float | ndarray | Series, dewpoint_c: float | ndarray | Series) → float | ndarray | Series[source]¶: Calculate wet bulb temperature from temperature and dewpoint.

Calculate Heat Index using the Rothfusz NWS equation.

Parameters:

temp_c – Air temperature in Celsius
rh – Relative humidity as percentage (0-100)

Returns:

Heat index in Celsius

varunayan.heat_stress.heat_index_from_dewpoint(temp_c: float | ndarray | Series, dewpoint_c: float | ndarray | Series) → float | ndarray | Series[source]¶: Calculate heat index from temperature and dewpoint.

Estimate Wet Bulb Globe Temperature using the Australian BoM approximation.

Closed-form WBGT from air temperature and humidity alone. Standard estimator in climate-epidemiology when wind/radiation are unavailable.

Reference: Australian Bureau of Meteorology approximation of WBGT (Steadman-based); see ACSM heat guidelines.

Parameters:

temp_c – Air temperature in Celsius
dewpoint_c – Dewpoint temperature in Celsius

Returns:

WBGT in Celsius

Calculate shade/indoor Wet Bulb Globe Temperature (ISO 7243).

Uses the indoor formula 0.7*Tw + 0.3*Ta. For a closed-form estimate from temperature and humidity alone, use wbgt_simple(); for outdoor WBGT with an explicit globe temperature, use wbgt_outdoor().

Reference: ISO 7243 standard for occupational heat stress.

Parameters:

temp_c – Air temperature in Celsius
wet_bulb_c – Wet bulb temperature in Celsius

Returns:

WBGT in Celsius

Calculate outdoor Wet Bulb Globe Temperature with solar load.

Reference: ISO 7243 standard for occupational heat stress.

Parameters:

temp_c – Air temperature in Celsius
wet_bulb_c – Wet bulb temperature in Celsius
globe_temp_c – Black globe temperature in Celsius

Returns:

WBGT in Celsius

Calculate Humidex (Canadian heat discomfort index).

Parameters:

temp_c – Air temperature in Celsius
dewpoint_c – Dewpoint temperature in Celsius

Reference: Masterson & Richardson (1979), Environment Canada.

Returns:: Humidex value (unitless, but interpreted like temperature)

Estimate mean radiant temperature from global horizontal solar radiation.

Closed-form radiation-balance estimator for a standard person from Thorsson et al. (2007), absorbing global horizontal shortwave onto the longwave radiant balance.

Reference: Thorsson, S., et al. (2007). Different methods for estimating the mean radiant temperature in an outdoor urban setting. Int. J. Climatol., 27(14), 1983-1993.

Parameters:

temp_c – Air temperature in Celsius
solar_rad_wm2 – Global horizontal solar radiation in W/m²
wind_ms – Unused; kept for backward-compatible signature. Wind enters the convective terms of UTCI/WBGT, not this radiant estimate.

Returns:

Estimated mean radiant temperature in Celsius

Calculate Universal Thermal Climate Index (UTCI) using polynomial approximation.

Reference: Bröde et al. (2012). Deriving the operational procedure for the Universal Thermal Climate Index (UTCI).

Parameters:

temp_c – Air temperature in Celsius (-50 to 50°C)
rh – Relative humidity as percentage (0-100)
wind_ms – Wind speed at 10m height in m/s (0.5 to 17 m/s)
mrt_c – Mean radiant temperature in Celsius. If None, assumes mrt = temp_c

Returns:

UTCI in Celsius

UTCI via sparse Legendre polynomial (Roman et al. 2025, doi:10.5281/zenodo.17465548).

Wider wind range than Bröde polynomial (0.5-30.3 m/s vs 0.5-17 m/s).

varunayan.heat_stress.heat_index_risk_category(hi: float | ndarray | Series) → str | ndarray | Series[source]¶

Categorize heat index into NWS risk categories.

Categories: - Normal: < 27°C - Caution: 27-32°C - Extreme Caution: 32-39°C - Danger: 39-51°C - Extreme Danger: >= 51°C

Parameters:: hi – Heat index in Celsius
Returns:: Risk category string(s)

varunayan.heat_stress.wbgt_risk_category(wbgt: float | ndarray | Series) → str | ndarray | Series[source]¶

Categorize WBGT into ISO 7243 risk categories for occupational heat stress.

Categories: - Low: < 25°C - Moderate: 25-28°C - High: 28-30°C - Very High: 30-32°C - Extreme: >= 32°C

Parameters:: wbgt – WBGT in Celsius
Returns:: Risk category string(s)

varunayan.heat_stress.utci_category(utci_val: float | ndarray | Series) → str | ndarray | Series[source]¶

Categorize UTCI into thermal stress categories.

Categories (10-level scale): - Extreme Cold Stress: < -40°C - Very Strong Cold Stress: -40 to -27°C - Strong Cold Stress: -27 to -13°C - Moderate Cold Stress: -13 to 0°C - Slight Cold Stress: 0 to 9°C - No Thermal Stress: 9 to 26°C - Moderate Heat Stress: 26 to 32°C - Strong Heat Stress: 32 to 38°C - Very Strong Heat Stress: 38 to 46°C - Extreme Heat Stress: >= 46°C

Parameters:: utci_val – UTCI in Celsius
Returns:: Thermal stress category string(s)

Calculate all heat stress indices at once.

Parameters:

temp_c – Air temperature in Celsius
dewpoint_c – Dewpoint temperature in Celsius
wind_ms – Wind speed in m/s (optional, needed for UTCI)
solar_rad_wm2 – Solar radiation in W/m² (optional, for outdoor MRT)

Returns:

rh: Relative humidity (%)
wet_bulb: Wet bulb temperature (°C)
heat_index: Heat index (°C)
wbgt: Wet Bulb Globe Temperature (°C)
humidex: Humidex value
utci: Universal Thermal Climate Index (°C) - if wind provided
heat_index_risk: Risk category for heat index
wbgt_risk: Risk category for WBGT
utci_stress: Stress category for UTCI - if wind provided

Return type:

Dictionary with all calculated indices