Generally speaking, that is.
What month do most California vineyards harvest their grapes?
What month do most wineries release their new vintages?
Wine grape harvest happens in the fall, concluding around mid-November. Wine releases occur every month; sometimes releases are delayed for readiness. Check out
htttp://www.winerelease.com
The grape harvest usually starts in early September, and may end as late as early October. Most wines seem to be released in September or October, but there are plenty of winter and spring releases too. Reds, anyway; I’m not sure there’s a favored season for white wines.