Although I live in the Eastvale/Corona area, I do work out there off and on.
The weather is always beautiful, but tends to heat up, a dry heat...Last year I loved it but many complained it was too hot. We wore jeans, brushpoppers and boots and yes we were a bit warm but perfect when the sun went down. The next day we wore shorts with flip flops and our hats, mainly due to the blisters!!
Expect it to be a dry heat in the upper 80's to 90's
Just my experience and opinion which doesnt account for much
Bring a sweatshirt for the night if it gets windy, like it did last year. I was glad I had one! But when there was no wind it was real nice at night. Problem is, as soon as that sun comes up (6:30??) it gets blazin hot in your tent, and sleeping was not easy at that point.