We get our hottest days in OC usually in the fall, when there is high pressure inland and a very slight offshore flow. Downslope compression and no sea breeze really cooks here. I was riding home about mid October 4 years ago. Riding thru Irvine on the San Diego creek trail (almost flat) about 13 mph my heart rate was 165, it was hot, yeah, but I didn't realize how hot. Stopped at a drinking fountain, filled and drank two bottles, filled it again and dumped it over me and set off for Lake Forest, about 7 miles to go with two full bottles. Had to stop in the shade near Costco and dump another bottle over me, drank the other one by the time I got home. Looked at the outside thermometer, it was 107. That's too hot!