IFSAC Wildland Pro Board Practice Exam 2025 – Comprehensive All-in-One Guide to Exam Success!

Relative humidity (RH) is typically at its lowest point during the mid to late afternoon due to several atmospheric factors. As the sun rises and daytime temperatures increase, the air warms up, allowing it to hold more moisture. This process reduces the relative humidity, as the amount of water vapor in the air stays relatively constant while the capacity of the warm air to hold moisture increases.

Throughout the day, sunlight heats the surface of the earth, causing evaporation from water bodies and moist soil, which initially increases humidity. However, as temperatures climb, the relative humidity drops, generally peaking later in the evening or early morning when temperatures are lower. Consequently, the peak heat of the day during mid to late afternoon correlates with the lowest relative humidity levels. Understanding this process is essential for predicting fire behavior and the effectiveness of fire suppression tactics in wildland firefighting scenarios.