My favorite it a rain cape. They don't get terribly hot and keep you reasonably dry.
Campmor has a cheap one, there are several others ranging from $35- $300, pick your fashion. The Campmor works fine, but I used it enough to wear out the water repellant within 3 years. I washed it and retreated it but I'm thinking of investing in a
Grunden's rain cape, they have a great reputation. For feet, I use Rivendell Splats which are convenient, effective and fit any shoes or pedals, they also have some gaiters for the lower legs which work well. All this revolves around keeping cool, I can't see the point in keeping rain off when you will be saturated with sweat.
Marc