Crickets

    And when lightning flashes nearby, counting the number of seconds ("one-one thousand, two-one thousand", etc.) until you hear its thunder will tell you how many miles away (one mile per every five seconds) it was.

    We did that a lot, during the Pennsylvania summers, when I was growing up.  Yes, we were easily amused back then.

Thunderbolts and Lightning

    We've been inundated two nights in a row by rain-soaking monsoons.  This calculation came in handy.