The rest of the nation has sweltered this summer, but California has escaped extreme heat -- until now. The National Weather Service may not have high-end graphics, but its map tells the story. The San Joaquin Valley, starting south of Modesto, is colored a brownish-red and that means excessive heat warning. Temperatures are expected to exceed 100 degrees every day until Tuesday. The bright pink areas indicate a heat "watch" (click here if you don't know the difference). This kind of heat is not just a weather story, it's a significant health and environment story too.