You aren't crazy and it definitely isn't thunder. I live in North Clearwater and have posted on this forum several times about hearing it too. One night it was so bad our windows shook. Last night it was on and off and kept me up until 1:30AM.

We were posting about it on the other thread here: Thread: Rumbling noise in sky around 2am last night, Clearwater, FL (Page 5)

I'm going to try to record it next time and hopefully catch it. There are videos on Youtube of it too: [link to www.youtube.com]