I am thinking about adding a window using 1/2" HC to the front, and trying to find an easy way to close and open. Maybe slide a piece of plywood from inside to close during winter.
Top-hinged windows act as their own awnings and can be adjusted for any degree of airflow.
But unless you've got weather blowing in directly you're unlikely to need to close up in your location (unless you're in high mountains and not the mild climate that saying "California" brings to mind for people who don't live there).
Chickens tolerate cold much better than they tolerate heat -- down to 0F and below when well-acclimated. You might find this thread reassuring: https://www.backyardchickens.com/posts/25324962