Actually Pizza, I checked the weather channels website and ran the averages, Fallbrook is quite a bit cooler than even your one day sample. There are always hot days or hotter than average years but the Average high temp in July and August is only 82 compared to Temecula’s 98 for those same months. Where the weather station is in relation to a town can swing it a couple of degrees as well.
One thing not mentioned about the brook is the fire danger. There is a benefit to multi lane roads and tract homes. Be sure wherever you look in Fallbrook that there is a fire hydrant very near your house, communities at an elevation without a natural water supply can have trouble during fire season (ask Ramona) and this county burns down every four years, so be wary in your selection if you are looking far from town in the hills.