Heat Waves in the US during 2012

Following the extended period of warmth in spring, during which 15 states set all-time March records, in some cases by large margins, a summer that rivaled those of the Dust Bowl era ensued. Widespread drought led to record heat extending over much of the lower 48 states, with several distinct heat waves leaving few parts of the country untouched. In late June, a broad upper-level ridge began to migrate eastward from northwestern Mexico, bringing excessively warm temperatures aloft (above 30°C at 850 mb across parts of the Great Plains, with 500mb heights nearing 6000m). This ridge brought record high temperatures to parts of Colorado, Wyoming, and Kansas. Over the subsequent days, the ridge slid slowly eastward, bringing record high temperatures in a wide swath from Missouri to South Carolina, including 43°C (109°F) at Columbia and Nashville, and 41°C (106°F) in Atlanta. The ridge expanded northward through the first week of July, bringing record heat to the Upper Midwest and Great Lakes region, with values exceeding 38°C(100°F) at most locations. Throughout the remainder of July and into August, positive upper-level height anomalies persisted over much of the country; while fewer absolute records were broken, anomalous warmth continued through the country, centered on the southern Plains, where Oklahoma City tied an all-time record high temperature of 45°C (113°F), amid a string of 7 consecutive days with high temperatures of 41°C (105°F) or higher, tying the record from 2011. The ridge oscillated westward by mid-August, bringing record heat from Arizona to Washington. Phoenix set a record of 7 consecutive days with overnight low temperatures remaining above 32°C (90°F). The extensive duration and spatial extent of the anomalous heat during summer 2012 took its toll on Americans' well-being as more than 100 heat-related deaths were reported. In many locations though, preliminary accounts of heat-related mortality were well below those of historical heat waves, such as the 1995 Chicago heat wave, suggesting that the greater awareness and intervention may have mitigated vulnerability to some extent.