Calculate temperature and humidity from wet bulb temperature Calculate wet bulb temperature from temperature and humidity
°C
Safe Caution Extreme Danger

Temperature & Humidity Relationships

Understanding the Risks

Safe Zone (< 19°C WBT)

Normal conditions where the human body can effectively regulate temperature through sweating. Most outdoor activities are safe.

Caution (19-25°C WBT)

Increased heat stress. Older adults and those with health conditions may struggle. Limit strenuous activity.

Extreme (25-31°C WBT)

Dangerous for vulnerable populations. Young healthy adults approach their compensability limit. Air conditioning becomes essential.

Unsurvivable (> 31°C WBT)

Beyond human adaptability. Even young, healthy individuals cannot cool themselves. Fatal without environmental cooling.

What is wet bulb temperature?

Wet bulb temperature is a critical measure that combines air temperature and humidity. It represents the lowest temperature that can be reached through evaporative cooling - essentially, how well our bodies can cool themselves through sweating.

Why It Matters

Recent research shows the human body cannot cool itself when wet bulb temperatures exceed 31°C (87°F at 100% humidity) - lower than the previously thought 35°C limit.

Climate Change

At 2°C of global warming, 35% of Earth's land area and billions of people will experience these dangerous conditions regularly.

Based on latest research: Penn State Study (2022) | PBS Terra Episode on Wet Bulb Events

It's important to note…

  • The 31°C limit applies to young, healthy adults. Older adults and vulnerable populations have even lower thresholds.
  • Activity level matters. These limits assume light activity; strenuous work lowers the threshold significantly.
  • Duration is a key factor. Prolonged exposure is more dangerous than brief encounters.
  • Air conditioning is the only solution. Once past the limit, shade, water, and wind cannot help.

Climate projections

At 2°C warming, likely by the 2040s, major population centers - including most of India, China, and the eastern U.S. - will regularly experience dangerous wet bulb events.

At 4°C warming, over 60% of Earth's land area could see uncompensable wet bulb temperatures. At this level, the vast majority of the world's population will be exposed to conditions that are beyond the human body's survival limits.