Wildland Firefighting Practice Exam

During what time of day do winds typically blow up canyon?

1. Morning

2. Midday

3. Evening

4. Night

The correct answer is: Midday

Winds typically blow up canyon during midday due to the heating of the earth’s surface. As the sun rises, it warms the surrounding land more rapidly than the air over the cooler canyon. This warming causes the air above the land to rise, creating a low-pressure area that draws cooler air from the canyon up and into the valley. This process is driven by a difference in temperature and pressure, resulting in what is known as an upslope breeze. It usually occurs most strongly in the late morning and reaches its peak during the early afternoon, making midday the time when canyon winds are most pronounced. In contrast, morning winds are generally more stable and typically flow down toward the valley due to cooler temperatures and the effects of nighttime cooling. In the evening and at night, the process tends to reverse as the land loses heat, leading to winds that blow down the canyon. Understanding these daily wind patterns is crucial for wildland firefighting, as they can significantly influence fire behavior and spread.