Sunburns are more than just a painful part of summer. They can damage your skin, cause cancer and otherwise do bodily harm. While not being burned in the first place is the best answer, once you've been burned, you're going to want to get over it as fast as possible.
Cool Shower : Like any burn, getting rid of the heat is the first priority. As long as it's still hot, it's still damaging your skin. You do not want to take a cold shower, that can cause a shock to your body. A lukewarm shower is the best. If you can, stay in it until the burn is totally cooled. In areas with water restrictions that might not be possible.
Vinegar Water : This is another way to help cool the burn. Mix one part vinegar to four parts cool water. As with the shower, do not use cold. Dip a soft cloth into the water, wring it out and lay it on the burn. This will have to be repeated many times and on all of the burn. The vinegar treatment is ideal if the person burnt can not stand for very long or as mentioned above, there are water restrictions.
Aloe Vera : This gel is great for burns of all sorts. It's best to buy it with the outer part removed, as it can cause pain. The skin has cactus like needles which are not helpful. Because the gel is mainly water, it's fairly safe to use even if the heat is not totally gone.
Lidocaine : This provides very short term relief from the pain. It is applied directly to the burn, often in either aloe gel or in a spray bottle. Do not use it more often than the instructions say.
On the Use of Butter
Whatever you do, do not put butter or any other oil based product on a burn that has not been cooled. It will seal the heat in and make the burn much worse. I know this is a remedy passed down from mother to daughter for centuries, but it is not a good idea. I've seen what happens when you do it, and it is not pretty.
When you Need Help : Some sunburns can be so bad you need medical help. If the burn covers more than 20% of the body, it's on a very young child or other symptoms accompaniment it, a the very least call your doctor. If there is nausea, vomiting, headache or other symptoms of heat sickness, call 911. They will give you instructions on what to do until help arrives.