He is not at high risk of having bad weather, but you are correct, which is why he already has a round trip ticket on the smoker in his pocket. At this point though, we're coming into the best "flying weather" part of the year between the coast and the mountains, and you can always go down underneath and fly out into the the desert through the passes. That's what's nice in most of California and the SW, you run into very few days that aren't flyable outside winter, and even that's mostly flyable.
I say do it even if it isn't practical. You have a commercial ticket in you pocket, so the worst you have to be out is some money and inconvenience fetching the plane later. But hey, that's part of the risk we sign up for when we sign up on GA. If you don't take a chance, then you will find little utility in having a pilots license. Most likely you'll make this just fine and you will figure out, "Damn, I need a faster plane with two engines." and do I have the girl for you...