Rainfall with no visible clouds in sight?

Dear Tom,
A while ago, it rained for a few minutes. I went outside to put the top on my car and when I looked up, there were no clouds. How is this possible?
William L., Gary, Indiana
Dear William,
On occasion, clouds causing rain are quite small and moving rapidly. This probably was the case in the situation you are describing. The rain fell from the cloud but by the time the drops hit your car and you had a chance to get outside, the cloud had moved on. This is not at all unusual. I’ve been outside when the sun was shining but rain was still falling from clouds that had already moved away. Small raindrops fall at speeds of about 10 feet per second. Let’s say the base of the clouds producing the rain was at 6,000 feet. At 10 feet per second, it would take the raindrops 10 minutes to reach the ground, plenty of time for the clouds to move away from directly overhead.

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