When it rains, but there are no visible clouds above you.
I stood outside and it was gently raining, yet there was blue sky above me. I was told it is called "immaculate rain". Immaculate rain and snow are signs of Spring in the high-desert.
(See also "Immaculate Snow")
Scientific info available at NASA website, astrobiology.
"Immaculate Rain"; precipitation occurring with no visible clouds directly above is a sign of Spring in the high-desert.