Dry ground has led to some wild temperature swings


"It's so warm out, but it was so cold this morning!" This is (more or less) what my wife said to me a few days ago.

These wild temperature swings we've seen lately are, in large part, due to the dry ground. As of Thursday, we have gone 21 days without measurable rain. That's one of the longer dry spells we've seen, since records started being kept in the late 1930s.

In those 21 days, the average spread from morning low to afternoon high is about 30° area-wide. For perspective, the average spread from morning low to afternoon high the rest of the year is about 22°.

Why such a large spread?

If there were more moisture in the ground, there would be a certain degree of evaporation. Evaporation is a cooling process, and thus limits how high the temperature can get after the morning.

With a dry ground, sunshine and high pressure in the upper levels of the atmosphere promoting dry air - the temperature can spike without evaporation having as much of a cooling impact.

Rain chances increase, though, by later this weekend. For details on that, check our latest forecast summary.

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