San Francisco is the kind of city where you need to leave your house prepared for weather at least three seasons worth of weather. It might be sunny and hot when you leave the door but windy and 15 degrees cooler when rounding the corner. And then fog turns into rain into sun. If you’re cold walking down one side of the street try crossing to the other side and see if that micro-climate is more in line with your preferences.
It may technically be summer here right now but it doesn’t mean that it doesn’t look like the other sides of the spring/fall bookends at the same time. Have I mentioned how much I love this city?