Coastlines are awesome at regulating temperature. That's why San Diego and LA can be so bearable in the summer as well as the winter. But the farther inland you go (even within the city) the hotter it gets.
The next best would likely be elevation, and if you are on mountains, you can try for the north face of the mountain in the summer. The sun will go down quicker, and rise later so it won't have as much time to heat up, and you could potentially be in partial shade most of the day from the mountain as well or trees, depending. That all helps a little to cool things down in the summer. lots of these little things can add up. But shade and solar power are not exactly best buddies, so if Solar is your only source of electricity(like me) that might be an issue.
There is more detailed answer here (
http://www.onthesnow.com/news/a/15157/ask-a-weatherman--how-does-elevation-affect-temperature-) but from that you can see:
"the temperature decreases by about 5.4 degrees Fahrenheit for every 1,000 feet up you go in elevation. In mathematical speak that is 9.8 degrees Celsius per 1,000 meters." - Joel Gratz (Meteorologist)
Personally I generally make a big loop from Washington/Oregon in the summer to Southern AZ in the Winter. But I have family in WA and AZ(and various other places along the way), so I have reasons to travel so far (tho it takes me a full year to make the trip, so I'm not remotely in any hurry).
One could spend the entire year in AZ and do just fine (and many of us do just that), the lower deserts around Quartzite and Yuma in the winter, and the north part of the state in the Summer (Flagstaff area for instance) and be relatively comfortable, and save a lot on gas/travel expenses.
Hope this helps!