This is SoCal- the season never ends unless you decide to stop.
Our normal track racing season starts the second or third week of January, traditionally driven by when we had World Cup events here. We usually had a big event the week after WC, when some of the riders would still be in town. Then the "regular season" starts in February, and transitions into all the various state and velodrome championship races (at 3 different velodromes) plus special events like Far West going into September, and then the racing season ends with Elite Nats in the first week of October. A couple years ago Encino had a crazy race in December that was $10,000 split 5 deep for the winner after 400 laps.
The main reason we don't have more after that is to take a break from having to organize it. We keep kicking around the idea of having a 24 hour madison some time in November. Regular race training (including tuesday and thursday night intervals and sunday madison practice) are year round except for holidays like thanksgiving, xmas, new years, etc. Check out the schedule-- the complete schedule of the last several years is still up.