Unless you need a city block covered then this will work for you. Get a piece of 1/2" EMT conduit, next every 1/2" mark with a sharpee where your holes will be and make sure there in a straight line, next using a 1/8" or smaller drill bit, drill the holes you marked and cut the EMT to about 6' or 7' section and crimp one end of the pipe, next take a garden hose and cut off one end and connect to EMT using a hose clamp be sure you don't cut off the end needed to fit your water inlet. Next for support go to Radio Shack and get 2, 3' tri pod mounts and 6, 5' sections of steel mast, using the tri pods has a base place the joined two sections of mast into the tri pod and use has towers the other two sections of mast will be used for a cross support, next hose clamp your EMT to the cross support with the holes facing up and just alittle to the side of your actors you may have to tilt your rain bar to get a even flow of water, next let the water flow and you have rain. You will have to play around with this to get the best shot but I think this just might work for you.
(Remember to back-light your rain to get it to show up)
Attach a cheap sprinkler head to a length of hose and affix the sprinkler securely to the top of a ladder, a pole, a tree, a basketball hoop, the roof of your house or wherever you can get it 10'-15' above the ground in the area where you'll be shooting. When you turn on the faucet, water rushes through the sprinkler head which broadcasts the water up into the air. As gravity takes over, the water droplets spread out and fall back to earth in a way that looks and sounds convincingly like genuine raindrops.
To make your rainy day more believable, mix in sound effects of rain and thunder from a sound effects CD when you are editing, or try playing them audibly near the camcorder while you are recording. To make your rain effect even more convincing, avoid shooting from an angle that shows bright blue sky in the background. You may find that shooting at dawn or dusk will help. In any case, it works best to shoot in a heavily shaded area, or through a gray lens filter to make clear skies appear dark and overcast. Stretching a black nylon stocking tightly over your lens is another way to make bright skies look more ominous. Just use a rubber band to hold the nylon in place. (By the way, this rain effect works quite nicely after dark. You'll need to be sure that you have enough light to shoot, but you won't need to worry about having blue skies in the background).
So why sit around waiting for Mother Nature to bring the weather you need for your next rainy day scene? Hollywood began using this effect to make rain years ago, now you can use it to create realistic looking rain on even the nicest of days. (originally in Videomaker magazine, September, 1998. Written by Chuck Peters)
Adapted from the book, "Camcorder Tricks and Special Effects."
Use a colander and a garden hose to simulate rainfall:
Cover your camera with a plastic bag, to be safe, then, position the colander in front of and above the lens of the camcorder (one to two feet away). Make sure the colander is out of frame.
Slowly run water through the colander to make rain. The water in the foregrounbd will make it look like it really is raining.
Many of the cloudy effects you see in Hollywood productions were actually done underwater. Here's how you can produce a similar effect:
Set a water-filled aquarium up in front of a sky-blue background.
Set up the camera's field of view so it points through the aquarium. Zoom in tight to leave plenty of room on the edges of the aquarium.
Fill the baster with milk, paint or ink. While being careful to keep both hand and baster out of the shot, inject the material into the water. With practice, you'll be able to create the appearance of billowing clouds and raging storms.
Place a fan just out of frame of your shot, and mess up your talent's hair to give it a wind-blown look.
Turn on the fan so it blows toward the talent.
Throw leaves in front of the fan so they will blow into the frame by the talent. This accentuates the visual effect of the "wind."
Have you talent wear a lightweight scarf or loose clothing to accentuate the effect, and with good enough acting on the talent's part, you can pull this off!
Adapted from the book, "Camcorder Tricks and Special Effects"
Have some assistants shake some tables from underneath them so that stuff falls off, have the actors act accordingly, and then shake the camera. Easy as pie.