A lot of people feel that when it's raining or snowing, extremely hot or cold, the camera automatically has to stay safely indoors. I do have to admit, that is a good way to protect your camera, but you end up missing some great shots.
On the other end of that spectrum, some people are careless about their digital cameras. They don’t think anything of leaving their cameras in stuffy car when the temperature outside is 100 degrees. All cameras hate extreme heat and extreme cold.
You invested hard-earned money into a digital camera. When the weather's bad, be it hot, cold or raining, you don't want your camera to be damaged.
Get a good camera bag
One thing you can do to protect your camera while traveling or hiking or exposed to the elements is to invest in a good, high quality camera bag. There are plenty of them out there and a lot of them are weatherproof. Bogen and Lowepro are two makers of quality bags.
Not only will a good bag protect your equipment from the weather, but they will also keep all that equipment you carry around safe and secure.
Use a UV filter
It's also a good idea to use a filter such as a UV (ultra-violet) or skylight filter to protect your lens. They’re much cheaper to replace then a lens any day of the week.
Rain tips for your camera
There are a few things you can do for your camera if you happen to be stuck outside with holding it, and weather really becomes a factor.
If the weather turns to rain, you can put your camera under your jacket, shirt, hat, anything that will shield it. If you’re interested in getting some pictures of the weather, you can put your camera in a plastic bag and make a hole big enough for the lens. Just use a rubber band to secure the bag to the lens.
How to beat the heat
Avoid leaving your camera in the extreme heat if you’re outside. Laying a light towel over it will help shade it from the sun. Don’t use dark colors, as they will just absorb the heat.
When it's cold outside
When its gets cold out, one thing you can do for your camera is try to keep it as warm as possible. Again, putting it under your jacket works well using, your body heat. Keeping your camera as warm as possible will hopefully prevent condensation from occurring.
If condensation does happen, open the battery and memory compartments, empty them and keep the compartments open until they dry out. Don’t take your camera back outside if there is condensation in/on it. It is possible it will freeze. (source: cameras.about.com)