It depends on your opinion of "Extremely hot", and where in the hills you are.
Generally, the San Fernando Valley is in the mid-90s to 100+ range in the summer. The City ranges from the 70s at the beaches to the low 90s in the Hollywood area.
This particular property is in the hills between the City and the Valley, so it's probably going to be a little bit warmer than the city, but cooler than the valley. You might get some of the breeze from the ocean, but not as much. If this property is in a section of the hills that shields it from the breeze, that can increase temperatures.
The bottom line is that it will probably be in the 90s on the warmer summer days (which makes for perfect evenings outside on that amazing deck with that glorious view). Compared to 100+ in the Valley, it's not what I'd call extremely hot... But if you're interested in spending $10million, and you're worried about the heat, I would be happy to show you some properties along the ocean that you might like :)
Good luck with your search!