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What does this calculator estimate?
At 32 C (89.6 F) and 60% humidity the wet-bulb temperature is about 25.8 C (78.4 F): high enough that the body struggles to cool by sweating. Wet-bulb above 25 C signals dangerous heat stress for outdoor work or exercise. Enter air temperature and humidity in the BoringToolsKit wet-bulb calculator to check your conditions.
- Sustained wet-bulb temperatures near 35 C are survivable for humans for only a few hours. (Source: NOAA National Weather Service)
- The Stull 2011 approximation is accurate to about 1 C across its valid range. (Source: BoringToolsKit calculation methodology)
- High humidity, not just heat, drives wet-bulb danger: sweat stops evaporating. (Source: NOAA National Weather Service)
How this calculator works
Formula
Stull approximation: Tw = T x atan(0.151977 x (rh + 8.313659)^0.5) + atan(T + rh) - atan(rh - 1.676331) + 0.00391838 x rh^1.5 x atan(0.023101 x rh) - 4.686035, T in Celsius, rh in %.
Worked example
At 32 C and 60% relative humidity, the wet-bulb temperature is about 25.8 C (78.4 F), which falls in the caution zone for outdoor exertion.
Assumptions to verify
- Valid for 5 to 99% RH and roughly -20 to 50 C air temperature (Stull 2011).
- Wet-bulb approximates the lowest temperature reachable by evaporative cooling.
Frequently asked questions
What wet-bulb temperature is dangerous?
Sustained wet-bulb above about 25 C signals serious heat stress; near 35 C is survivable for only hours.
Why is wet-bulb worse than regular temperature?
It measures evaporative cooling limits: humid air blocks sweat from cooling you.
Cite this tool
BoringToolsKit. “Wet Bulb Temperature Calculator.” boringtoolskit.com/wet-bulb-temperature-calculator/. Free to reference in articles, syllabi, and answer posts with a link.
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