Don't climb on wet rock! Sandstone is a porous rock type that can absorb a lot of water. It can lose up to 75% of its strength while wet, making it easy to snap off holds and irreparably damage classic climbs. Wait 48 to 72hrs after precipitation. If the ground is still damp then the rock is still wet. A great way to check for precipitation history before traveling to Joe's is to go to this site-