I use Wunderground.Com for my weather info. I generally don't even bother with worrying about the weather unless the chances of participation is greater than 60%. Even when it does, there are several things you can expect. If you know the weather pattern in your area, then you can almost know what to expect. Here in the Bay area, the Northern part will gets the rain first most of the time before the southern area gets hit and we also can expects to have more total rainfall. There are other certain area that get more rainfall just because of the nature of the location. Another thing to look for is that here the weather is very unstable during the tail end of the storm and that's when it gets cold and rain cell develop. So try to learn as much about the nature of your area and it will help you a lot.

How much do you want to invest in rain gear is up to you. You can easily go overboard with high end stuff like Showerpass Jacket and whatever, but there are plenty of cheaper alternattive. I used the Performance Ultra Rain jacket and it perform extremely well under heavy downpour. I own both the Showerpass and the Perrformance Ultra and it work just as well but without the extra cost. If you wait for a sales and get it with their member discount, you can get it out the door really cheap. As for the leg, you can get a rain pant and use it as is or cut it off at the knee so that it has much less restriction and breathe better. I made a thigh gaitor that cover only my thigh area which is all I really need in that area of my leg. For the shoes to the calves area, I just use a $20 gaitor. Much more comfy than a rain pant and breathe much better.

It can be a turn off in the begining to ride in the rain, but once you get setup, it is really not that bad at all. Most driver thinks I'm a weird or crazy women for riding in the storm, but they generally gives a lot of positive cheers for doing it.