California’s biggest agriculture area is mostly fed by the Sierra mountains snowpack. Warm winters where the snowpack doesn’t build up are worse for the water situation that cold winters.

Part of what made California’s agriculture so successful was that you could control how your crops got water, rather than relying on the weather to provide rain. With reservoirs silted up, dams beyond their planned limits, and consistently warmer winters the water situation isn’t as robust as it was and I can’t see it getting any better.

Edit - source is only that I lived there, no professional expertise.