Originally Posted by Hornet
When is the best time to ride in California and Mexico?
For much of California, all year is fine. But the Sierra will be closed from about December to April in places. Coastal areas are mostly always mild save the odd heat wave (now). But that does not mean all of Summer is lost. California probably has the best riding weather, over all, in the world.
The Desert is another story. From May to late Sept. it can be dangerously hot. This includes California's Central Valley which runs from Mex border to Oregon and beyond. H O T !! So when its hot, either ride the coast or the mountains. But by Sept. it starts to cool and often you can ride through Winter. It can snow in the Desert too and flash floods happen.
Mexico is another deal, well described by DLbitten above. One thing is, don't forget the rainy season. May to November, roughly. Mostly in the tropical and sub tropical areas. Mostly rains in PM hours or at night. If you must make miles, ride early AM till rains come. If a BIG tropical storm hits, stay put for a few days.
Overall, for much of Mexico, October and November are best. Highlands October, November everyplace else.