Graph: California Day and Night Time Heat Waves

 The graph shows heat wave activity since 1950. The red line is based on maximum temperatures and the blue line is based on minimum temperatures. Degree days are the sum of degrees that exceed the 95th percentile of daily temperatures during June, July and August. The bold parts of the graph indicate when the heat wave activity is accentuated in minimum or nighttime temperatures (blue) or during the day (red), predominantly humid or dry days respectively.