During which part of the day do upslope winds generally peak?

Upslope winds are typically influenced by the heating of the earth's surface throughout the day. These winds occur when the air at lower elevations heats up due to sunlight, becomes less dense, and rises. As the sun's intensity increases, the temperature differential between the valley floor and the mountains or hills becomes most pronounced in the mid-afternoon. This is when the upslope winds are at their peak, as the thermal activity enhances the vertical movement of air.

In contrast, during early morning hours, the temperatures are cooler, and the thermal activity is less pronounced, leading to weaker upslope winds. By late evening, as the sun sets and the earth cools, the driving force behind these winds diminishes, and winds tend to stabilize and calm down rather than peak. The option suggesting that upslope winds are present all day long overlooks the pronounced peak typically seen in the mid-afternoon due to increased solar heating.