Look for spawn suppliers close to your climate or look for ones that supply a wide variety of strains suited to different climates. There are different ways to rack/stack the logs depending on temperature and humidity (see hendi_alex's example in his SC garden). I put mine on "rails" because we typically have drought in the summer and severe freeze in the winter.
In California, I think I would look to Fungi Perfecti (fungi.com). Two other sources I've considered in the past are Field and Forest (I think) in Wisconsin and Mushroom Mountain in one of the Carolinas (maybe SC).
Today, I ran outside to retrieve and replace the compost bin lid that got blown off by overnight gusty winds and discovered a wonderful surprise!
I saw the little bump in the lower part of the top photo first, and starting turning over the logs to examine them. The top photo shows my discovery of the big shiitake cap underneath one of the logs.
Middle photos are close up of the big cap shiitake and after harvesting. The little one got knocked off when I was turning the logs.
Bottom photo shows more little buttons that are growing. Hopefully they will be able to mature -- it should only take 3-4 days at most and it rained a bit today which should help.
I think the only reason I have this much to harvest in the same season as starting the logs like this is because of the abnormally warm temperatures we've been having. I think ordinarily, I couldn't expect to see harvest until the following spring, even though I did use a fast maturing and cold hardy strain for my spawn.