Riding in the rain has it's own bizarre appeal. Mostly it just makes me feel... tough. Like the pros

Hi-viz yellow apparel is good. Also remember to pack arm warmers (you'll chill more quickly when wet) and a blinky. I have at least one blinky on my road bike at all times for getting caught in the rain/fog/dark. Recently I put a tiny LED red blinking light in one of my rear helmet vents as well.

Watch out for paint and metal (grates and manhole covers). These become very slippery when wet. Feather your brakes to shed water and grime off of the rims before you need to stop. If you do crash in the rain, its not so bad. You just kind of slide around