As you can see, two people already said just in this thread they have 100% occupancy during the hot time.

Winter's are cold and summers are hot in northern Cali. 

Rentals have remained pretty hot outside of common slower times around holidays.

My 8 year old turns air bnb with my wife. 

This area definitely gives you good weather year round, summertime gets hot so as long as you're getting systems serviced before then and then in the fall you're usually ok. 

Timing is key—catch a hot market or a great 1031 exchange opportunity.

Use of Euro-style wall units for air-con.. 

As a sidenote I see people doing this and jacking up the price of the home to seller finance to above market value - if you do this you better be VERY clear with your investors that you are writing a $300k loan on a $250k property as if you do not you can get in some serious hot water later on down the line when doing valuations of the company. 

The hot tub gets all the praise haha. 

There is a river of hot water by the hotel Tabacon in San Carlos that is an absolutely unique experience.