A blistering heat wave is baking the western United States, the latest to blast the northern hemisphere in a summer that has brought extreme temperatures across Europe, Asia and North America.Climatologists say the kiln-like conditions in California, Nevada and Arizona are caused by a heat dome -- a...
A blistering heat wave is baking the western United States, the latest to blast the northern hemisphere in a summer that has brought extreme temperatures across Europe, Asia and North America. Climatologists say the kiln-like conditions in California, Nevada and Arizona are caused by a heat dome -- a huge bubble of stationary high pressure that is trapping ever-hotter air. And, they say, human-caused climate change is making these oppressive heat waves worse -- hotter, longer and more frequent. Here's what you need to know about heat waves. What is a heat wave? Anyone suffering through sultry nights and sweltering days knows they're in a heat wave, but there are a few technical definitions. The one the US government chooses is: at least two consecutive days when the minimum temperature for the area is hotter than 85 percent of July and August days in the same area, based on historical averages. That minimum usually comes at night, which is important -- after a very hot day, our bodies tend to cool off at night. But if the temperature remains elevated, that's much harder. This is when people get ill. It's also important to localize the definition. People accustomed to 85 Fahrenheit (29 Celsius) days are likely not fazed by 90 degrees. But if you live in a chilly, damp spot and the mercury hits 90, you'll find it much harder to cope. What causes heat waves? Generally it's an area of high pressure that parks itself in one spot, forming a heat dome --…