Working in foul weather is unpleasant, especially if you get soaked through your clothes in chilly temperatures. After much trial and error, I have finally found an appropriate way to dress that allows me to work outside in a downpour and stay relatively dry. I did have to sacrifice fashion for function, however!
I dress in layers so that I can add or take off clothes as needed. The key to staying dry is to have a long enough outer coat that keeps your legs protected as well as a hat that channels water away from your body. A full length saddle slicker solves the problem quite well. It provides coverage from shoulders to mid calf, and if you wear high waterproof boots, you will stay fully dry. I wear the outback style hats that allow water to drain away from your neck in heavy rains.
Don't expect this to be seen on the runways of Milan anytime soon
Traditional Oilskin Slicker
Less expensive version for messier applications or to keep as a spare