Nectar Flows in Northern California?

[Oyster]

Are there distinct nectar flow periods in the San Francisco Bay Area? This is my first full year of beekeeping, and I remember checking my lone hive (I now have three) that I got in August of last year, for the honey situation in September, and did not have more than 70% of the frames capped at that time. I did not check again, until I noticed swarming activity early this March, at which time the super was completely filled. This led me to believe that there is a secondary late summer/early fall nectar flow in this region. I'd like to know what the primary spring/summer nectar flow period is, or is it more or less continuous from spring to fall?

Thanks,