Sept. Temp and PM-10 Data Released
This September’s PM-10 particulate air pollution levels were higher than levels in July and August. September was also the second-warmest month for daily high temperatures in the last 19 years of Aspen’s record. 

“This is somewhat unusual because September usually has very low PM-10 levels,” said Lee Cassin, director of the City’s Environmental Health Department. “I suspect it was due to all the hot and dry weather, as well as all the traffic in town from leaf-peepers and the many special events we had this September.”

PM-10 levels followed the typical pattern of increasing through the work week (due to traffic) and dropping over the weekends (when traffic is much lower). PM-10 in Aspen is caused almost exclusively by traffic on high PM-10 days. PM-10 is thought to be responsible for tens of thousands of deaths a year in the US, including at levels sometimes experienced in Aspen.

Average September temperatures keep getting warmer with each time period – with this September being warmer than even recent past averages.

“This September was also very dry in Aspen with less than an inch of rainfall,” Cassin said. “Colorado had its fifth warmest September on record.” 

Nationwide, the warm season (April – September) had among the most extreme weather events on record, with some areas experiencing droughts while others had record precipitation. Different parts of the country also had different temperature extremes, with some places very hot and some cool. The official thermometer in Los Angeles broke after reaching an all-time high of 113 in September.

For more information on air quality in Aspen, visit For information on Aspen’s global warming programs, go to



Posted on Monday, October 18, 2010