Rain may be good for the garden but it's not something most photographers are fond of. However, if you find yourself in your car, on route to a landscape location when the heavens open, all is not lost as you can use your car as a canvas for shooting water drop abstracts.
If you have your macro lens in your camera bag grab it as it'll help you get closer to small groups of waterdrops. For those who don't tend to carry a wide variety of lenses with them a zoom lens will be fine so long as you use it at its minimum focus distance. A polarising filter can help cut down on reflections but on cloudy days you may find you don't really need one. Working hand-held is much more practical and as shutter speeds won't be too low, shake shouldn't be too much of a problem.
You can shoot droplets that have landed on the bonnet of your car or do as David Pritchard did and keep dry by shooting from inside the car.
If you do this, try and angle your camera so the background isn't too distracting. In the following shot, David used the sky as his background to create a graduated toning effect to this image.
Photo by David Pritchard
"It's a simple abstract that was shot from inside of the car as the clouds wouldn't have been much of a background for landscapes on that particular day," said David.
You may need to position yourself so you're not reflected back in the shot, use a small aperture (David used f/7.1) and if you find your shutter speed is creeping towards the slow side, use a slightly higher ISO.
Try experimenting with focal lengths and move your lens around the surface to capture a variety of different shapes and sizes of water droplets.