There is 94 percentage chance of rain and 9 mph winds from the Northwest. 3am:The San Luis Obispo, CA forecast for Mar 23 is 48 degrees and Overcast. There is 94 percentage chance of rain and 9 mph winds from the Northwest. 6am:The San Luis Obispo, CA forecast for Mar 23 is 50 degrees and Cloudy. There is 93 percentage chance of rain and 8 mph winds from the Northwest. 9am:The San Luis Obispo, CA forecast for Mar 23 is 53 degrees and Partly cloudy. There is 86 percentage chance of rain and 9 mph winds from the Northwest.