What time of day is generally the coolest?

The time of day that is generally the coolest occurs after sunset. This phenomenon occurs because, during the day, the sun heats the earth’s surface, which in turn warms the air above it. After the sun sets, this heating effect diminishes, leading to cooler temperatures as heat radiates away into the atmosphere.

At night, especially before sunrise, temperatures can drop significantly, but shortly before dawn is often when the air temperature is at its lowest. However, the period immediately following sunset typically contains much cooler temperatures compared to the warmer conditions experienced during late morning or midday, when the sun is at its highest and most intense. Thus, after sunset is considered the coolest time of day due to the absence of the sun's warming rays.