How to find out average sunshine across the US..

Is there a good URL?

[blaze]

I'd like to correlate website sales to weather in the US (and elsewhere) .. is there a good site to do this?

The weather must be pretty good today ..

[bird]

Depending on the exact type of data and also on the granularity you need, you might want to search for "test reference year" (TRY) data. Some of that may be available for free, others you may need to buy.