Spring 2018 was one of the hottest markets in SF and the Bay Area in the last 2 decades. Then the market began to cool in summer and autumn - demand, sales and appreciation rates generally dropping, while supply and price reductions increased - before the mid-winter doldrums took hold. The magnitude of these changes varied by county, with SF less affected than many others, but still certainly affected.
Since the recovery began in 2012, spring has typically been the most active season of the year, and usually the period during which appreciation gains have been the largest. The spring 2019 market is just getting started amid a diverse set of economic indicators. Financial markets have, so far, recovered in 2019, interest rates have dropped, and big local IPOs loom. We will know much more soon.