For a quick answer, I'd suggest you contact your local extension office. My guess would be that today is not the day to do it.

Here is a link that might be useful: Find your Extension Office link

Clay is composed of very fine particles of soil, tightly compacted. It does not absorb moisture readily during heavy, brief rainfall, unless the water stands in pools or puddles. The percolation rate is extremely slow, and unless you experience several days of continous rainfall, the soil beneath a top layer of a few centimeters, will only be slightly moist, maybe even dry, as we have experienced a 3" average rainfall deficit during the previous 2 months. If the area has not been tilled and/or ammended within recent years, I think you are safe in weekend planning.
Rb

Since the rain can only penetrate about 3 inches or so, I suggest you dig some now, and let the rain soften the earth farther down.

I do this with a hose during the summer if I need to dig. Dig, water, dig water, dig.......

Now. I like to work the clay when it is very wet or very dry. The inbetween is the problem.
When it is wet, it is softer and easier to dig. The only problem is that it sticks to your shovel or spade.
When it is Very dry, it is crumbly and easy to work as well.
The rest of the time I hate to mess with it.