Climate Highlights — Summer 2011
The average U.S. temperature during the summer of 2011 was 74.5 degrees F (23.6 degrees C) — 2.4 degrees F (1.3 degrees C) above the long-term (1901-2000) average and the second warmest summer on record.
The unprecedented heat during the summer period (June-August) of 2011 across Texas, Oklahoma, New Mexico, and Louisiana resulted in these states having their warmest summers on record. Average temperatures for the summer in Texas and Oklahoma, at 86.8 degrees F (30.4 degrees C) and 86.5 degrees F (30.3 degrees C), respectively, exceeded the previous seasonal statewide average temperature record for any state during any season. The previous warmest summer statewide average temperature was in Oklahoma, during 1934, at 85.2 degrees F (29.6 degrees C).
During the summer, a persistent ridge of high pressure bestrode the eastern U.S., causing warmer than average temperatures east of the Rockies. Fifteen states had a summer average temperature ranking among their ten warmest. West of the Rockies, a persistent trough brought below-average temperatures to the Pacific Northwest, where Washington and Oregon were the only states across the lower 48 to have below-average summer temperatures.
Based on NOAA's Residential Energy Demand Temperature Index, the contiguous U.S. temperature-related energy demand was 22.3 percent above average during summer. This is the largest such value during the Index’s period of record, which dates to 1895.
During the summer of 2011, all states across the contiguous U.S., with the exception of North Dakota and Vermont, experienced at least one day with a location having a daily maximum temperature exceeding 100 degrees F (37.8 degrees C). A large swath of the Southern Plains and Southwest had over 30 days with a daily maximum temperature of 100 degrees F (37.8 degrees C) or warmer.