I spent a productive couple of hours putting a scratch coat of render on the garage walls this afternoon. Nah - it won't rain, and even if it does it wont' be heavy enough to do any damage. A few pock marks won't hurt on a cratch coat.
Famous last words!
The wind suddenly blew up and the heavens opened, so, even after covering everything with tarpaulins, most of my render washed away.
This is the interesting pattern on one of the walls as a result.