OP, like yourself my afternoons are my time to ride. I've not been riding much this summer due to the afternoon storms that regularly come up. But this past Friday I told myself to get over it and, while there were rain clouds on the horizon there wasn't any thunder or lightning in evidence. Know what? Turns out riding in the rain is a lot of fun. And it beats the heck out of the 100+ degree heat and humidity that is the only other option for a Louisiana afternoon. I found myself wishing for some rain on the rest of my rides this weekend. And I kind of did feel like a bad ass, too.
Edit: Sorry, I re-read the post and realized you already said you wouldn't have a problem riding in the rain. With that, no, I wouldn't ride with active lightning. I would second the suggestions to stay close to home and perhaps just ride several laps of a short course if possible in case storms come up quickly. Not terribly helpful now, just my 2 cents.