Wet Bulb Temperature
Calculator
Results
- Wet bulb temperature (°C)
- 22.296833
- Wet bulb temperature (°F)
- 72.134301
- Wet bulb depression (°C)
- 7.703166
Weather results
| Wet bulb temperature (°C) | 22.296833 |
| Wet bulb temperature (°F) | 72.134301 |
| Wet bulb depression (°C) | 7.703166 |
formula-map diagram
- Wet bulb temperature (°C)
- 22.296833
- Wet bulb temperature (°F)
- 72.134301
- Wet bulb depression (°C)
- 7.703166
Weather relationship
Formula
Tw = T×atan(0.151977×√(RH+8.313659)) + atan(T+RH) − atan(RH−1.676331) + 0.00391838×RH^1.5×atan(0.023101×RH) − 4.686035= 22.29683396268
Note
This is a simplified model: it applies the published standard formula to the numbers you entered and ignores local terrain, radiation, precipitation type and instrument error. Wind chill is the 2001 NWS/Environment Canada regression, valid at or below 10 °C with wind at or above 4.8 km/h; the heat index is the Rothfusz regression, reliable above about 27 °C; dew point uses the Magnus approximation (a = 17.27, b = 237.7 °C) over liquid water; wet bulb uses Stull's approximation at standard sea-level pressure; pressure and density altitude assume the International Standard Atmosphere and dry air. Do not use these results for aviation, structural or safety decisions without an official forecast or a qualified professional.
More in Weather and climate
See all →Frequently asked questions
What is wet-bulb temperature physically measuring?+
Wet-bulb temperature is the lowest temperature air can be cooled to by evaporating water into it at constant pressure, traditionally measured with a thermometer whose bulb is wrapped in a wet wick and exposed to airflow. It reflects how much cooling evaporation can provide under current conditions.
Why is wet-bulb temperature always lower than or equal to the actual (dry-bulb) air temperature?+
Evaporation always removes heat from its surroundings, so a wet thermometer bulb cools below the ambient air temperature as water evaporates from the wick. The two temperatures are only equal when the air is already fully saturated (100% relative humidity), since no further evaporation, and thus no further cooling, can occur.
Why does wet-bulb temperature matter for extreme heat safety?+
The human body cools primarily through sweat evaporation, which becomes ineffective as wet-bulb temperature approaches body temperature, since the air can no longer absorb much additional moisture. A wet-bulb temperature above roughly 35°C is considered a threshold beyond which the body may not be able to cool itself even in shade with unlimited water, regardless of how hot the dry-bulb temperature reads.
How is wet-bulb temperature calculated without physically measuring it?+
From dry-bulb air temperature and either relative humidity or dew point, using psychrometric equations that model the evaporative cooling balance point, essentially working backward from how much drier air 'wants' to absorb moisture.
Why is wet-bulb temperature different from heat index for describing dangerous heat?+
Heat index estimates a subjective 'feels-like' value assuming shade and light wind, capped at what a person experiences; wet-bulb temperature is a physical limit on evaporative cooling itself, useful for extreme conditions and industrial or athletic heat-stress thresholds where heat index tables no longer apply.