Here is a listing for the Farmers Market in Shasta County. Starts April 3rd.
For Trinity County, I didn’t find a website, but i found a Facebook page, if you are interested in that Farmers Market. It is every Wednesday starting at 4pm
Chico has a market on Saturday and Thursday, both located downtown, in addition to other days.
Below is the California Certified Grown Farmer’s Market you do a search to find local market’s in each city.