We just got back from a quick trip to California to see kids and grandkids. It's so funny for me to visit California and feel cold, but that's what living in the desert has done to us. It's definitely cooler there in northern California than here in southern New Mexico, but the humidity also makes a big difference.
For example, today (I'm writing this on Monday, May 30th) it was 90 degrees F. at noon with 14% humidity here in New Mexico; where we stayed in California, a bit north of Sacramento, it was 68 at noon today with 50% humidity. We are long past needing any sweaters at home--we threw a couple into the suitcases before we left, almost as an afterthought, and wore them constantly. When we went out to the coast (today the temp there is 56 degrees, with 71% humidity) we couldn't have done without long sleeves.
Even though the weather in California is cooler at this time of year than ours, it is much more temperate year round than in our high desert--so we see plants in the ground there that we are used to keeping in pots and taking in during the winter. I had forgotten that in my childhood in San Francisco the geranium bushes in our front yard were almost as tall as my childhood self, so it all came back to me when we admired other people's gardens on our morning walks.
Of course, I had to stop and take some photos of a stranger's house where I saw geraniums growing right there in the ground. And my stepdaughter tells me that the roses in her yard grow like weeds without any special feeding or care.