1. Update Design Data
As recently at 2025, the Title 24 Reference Appendices provide design data for California which is based on:
"ASHRAE Climatic Data for Region X, Arizona, California, Hawaii and Nevada," Publication SPCDX, 1982 and “Supplement,” 1994
This is interesting because the data is, at minimum, over 30 years old and at this point, in relation to Climate Change, its validity is debatable.