Soil is dry enough to work when poking a finger into a fistful of it makes it crumble. If water comes out or your finger just makes an indention, keep waiting. It will dry out soon.
If you have already planted your garden and are worried about standing water, the plants should be okay if the area drains within 24 hours. For more information on what to do for vegetables, turf, and trees in flooded areas, read the K-State fact sheet on Flooding and Plants.