It was looking like a cool summer in Los Angeles until a couple of weeks ago.  Temperatures in downtown LA topped 90 degrees Fahrenheit only once this summer until September 25th.  Since then, according to the National Weather Service’s Climatological Report, the city has seen 4 days above 90, including today. Which is what a group of university and NASA scientists say Southern Californians had better get used to.  

The scientists analyzed 100 years of temperature data collected in downtown Los Angeles  and found that between 1906 and 2006 the average number of extreme heat days – those over 90 degrees – increased from 2 per year to more than 25 per year.  In that time, the average maximum daytime temperature for the city climbed 5 degrees.  Heat waves have also increased, from 2-day events to sweltering stretches that last for 1-2 weeks. The scientists predict that in the coming decades, 10-14 day heat waves will be the norm. 

The bottom line? Even though this summer was a cool one, Southern California is going to get warmer, for longer periods of time. “Our snow pack will be less, our fire seasons will be longer, and unhealthy air alerts will be a summer staple” said study co-author Bill Patzert, a NASA climatologist and oceanographer.

The scientists assert that the main cause of this increase in temperature and heat days in Los Angeles is due the “urban heat island effect,” which makes urban areas 2-10 degrees Fahrenheit warmer than the surrounding rural areas.

Check out a historical temperature chart for downtown Los Angeles and a full report on the study here.