We've had rain almost every day for a week. Yesterday I had the day off, and the weather also took a break, with sunny skies and temperatures in the 70s (F). Seems like perfect digging-in-the-ground conditions to me.
The area of activity is much larger this year than last. I wish I had a video camera. In the area of this photo, there were at least 30-40 bees flying around, but I can't pick them out from the photo at this scale and resolution.
Related ContentColletes thoracicus (Colletidae), Cellophane Bees, 2008-05-26
Flickr photo set