Posted September 16, 2007
A rain can really cool things off in Colorado. The air near the surface is usually on the dry side. The moisture that produces the rain often falls from high aloft this time of year. The rain falling into the dry air promotes evaporation. Since evaporation is a cooling process it can cool off significantly when it rains. Notice in the image below that the temperatures in eastern Colorado are in the 90s. Dry air, sunny skies and south winds promote warm temperatures this time of year. The low dewpoint though helps it feel not quite as hot as it would feel if the dewpoint was high. Notice the much cooler temperatures in the Denver area and in the mountains (western Colorado). The higher elevations will be cooler. Add rain falling into the dry high elevation air and the temperature cools off significantly. The second image shows the radar. It shows where it was raining at the time the temperature image was taken. Notice the rainy areas are much cooler than the non-rain areas of eastern Colorado. The last image is of the rain at the Habytime apartment on the same day. A hot day in Denver will turn much cooler very quick when rain arrives.