Just driving from Pasadena to Northridge and back this evening, we drove by 8 accidents and one stalled car, and almost became a statistic ourselves a couple of times.
Remember: Any change in speed or direction loses traction. Hitting your brakes AFTER you splash into a big puddle and start hydroplaning is TOO LATE! Just hold the wheel and stay off the pedals. Don't drive faster than you're capable of handling, and leave room to react to those who are driving too fast.
Be safe and I'll see you on future rides!