A 20-degree change in temperature causes relative humidity to change by what amount?

A 20-degree change in temperature causes relative humidity to change by what amount?

• A. 50%
• B. 10%
• C. 5%
• D. 0%

Answer: (A)

Rel relative humidity responds strongly to temperature when the amount of moisture in the air stays the same. Warm air can hold more water vapor, so increasing temperature without adding moisture makes the air’s relative humidity drop significantly. A common quick-rule in fire weather is that a 20°F change in temperature changes relative humidity by about half. So, if the air is around 60% RH and warms by 20°F, the RH would drop to roughly 30% (about a 50% reduction). The exact starting humidity matters, but the action is a large, roughly 50% change. The other options imply only small or no change, which doesn’t reflect how RH behaves with a temperature increase.

Rel relative humidity responds strongly to temperature when the amount of moisture in the air stays the same. Warm air can hold more water vapor, so increasing temperature without adding moisture makes the air’s relative humidity drop significantly. A common quick-rule in fire weather is that a 20°F change in temperature changes relative humidity by about half. So, if the air is around 60% RH and warms by 20°F, the RH would drop to roughly 30% (about a 50% reduction). The exact starting humidity matters, but the action is a large, roughly 50% change. The other options imply only small or no change, which doesn’t reflect how RH behaves with a temperature increase.