I'm not an expert, but I believe this to be an altocumulus formation, a precursor to thunderstorms later in the day if seen on a warm and humid summer morning, our exact current conditions.
If it proves true and the sky turns dramatic this afternoon, I'll try to post more images.
|Close-up of altocumulus. The black points in some of the clouds|
are swifts, darting about the sky on their early morning food run.
Click on the photo to see a larger image.