One of the first things a new vegetable gardener has to learn is about cool weather crops and warm weather crops.
Cool weather crops are very cold hardy and frost tolerant, do well in cool to cold weather and tend to fizzle out when it gets hot. This includes all the brassicas (broccoli, cabbage, cauliflower etc), most root crops, peas most green leafies like lettuce and spinach. So it is either too late or too early to plant lettuce and peas. Too hot now for them. You can plant them in early spring, Mar or April (probably Feb or Mar, as soon as the ground can be worked, for peas), and you can plant them at the end of summer, Aug or Sept for fall crop.
Warm weather crops like warm to hot weather and die if they get too cold or especially if they get frosted. That is pretty much everything else. But there are degrees of it. Corn is the earliest of the warm weather crops, then tomatoes, then peppers and beans, then all the cucurbits (squash, melons, pumpkins, etc), which can't go in until the soil is well warmed up.
But the other variable in there is how long it takes to produce. Beans you could still plant as well as summer squash. Peppers would grow if planted now, but they take a LONG time to produce (from seed at least four months maybe more). That's why Peter said too late for peppers - you wouldn't have time for them to produce. Likewise winter squash and the larger watermelons. Dwarf watermelons like Sugar Baby you may still have time to get fruit from. Sugar baby has a days to maturity about 80 days (that is time from when seedling is transplanted into garden until first fruit). So if you know your average first frost date, you can count backwards from it to see if you still have time.
(If you don't know your frost dates, you can put your zip code in here https://www.almanac.com/content/frost-ch ... -states/CA
and it will tell you).
Let us know how it goes for you! Best Wishes!