Last October I planted crimson clover that turned out great! It is about knee to thigh high now and I was wondering if I should trim it or leave it as is?

I always cut mine just before it heads out sounds to me like you are way past due H H

Haha I'd say so! Should I wait for a rain chance before cutting it?

cut it to about 4 inches now

I don't know about crimson clover, but I only cut my ladino clover to knock back any weeds threatening to crowd it out.

Cut it quick. Very heavy seeding clover that is low in attractiveness. Mostly a spring grower and hard to get rid of one it seeds. Stick with the white clovers.