Preliminary Observations of Extreme Temperatures and Heat-Related Illnesses in a High Plains Canyon Environment

Palo Duro Canyon is the largest of several eroded canyonlands along the eastern terminus of the southern High Plains Caprock escarpment in west Texas. Measuring 100 km in length, Palo Duro is the second longest canyon system in the USA and home to Palo Duro Canyon State Park- a nature conservatory which recently topped Fodor's Travel list of America's 10 Best State Parks and host to more than 300,000 outdoor enthusiasts annually. Most tourists visit the park during summer, and 104 incidents of heat-related illnesses/deaths have been reported in Palo Duro Canyon State Park since 2011.

This study documents preliminary observations of extreme temperatures recorded by two meteorological instruments deployed along the canyon floor prior to the summer of 2014. These thermometers provide measurements near park trailheads where a majority of heat-related incidents occur. The relationship between daytime high temperatures on the canyon floor and those observed at established sites on the adjacent High Plains is shown to be linear (R²=0.95), with differentials frequently reaching 5° to 6° C. These observed temperature variances are more than double expected rim-to-floor differences attributable to the 232 m elevation change via adiabatic processes. Correlations observed in these data are used to determine approximate temperatures associated with past heat related-incidents. Linear regression models support temperatures that approached 50° C during a record setting heatwave in June 2011 when 25 persons were treated for heat exhaustion. Such temperatures estimated to occur at 867 m ASL in Palo Duro Canyon are comparable to record high temperatures of 49° C observed at the 776 m Phantom Ranch in Grand Canyon National Park. Statistical signals seen in the preliminary observations and historical trends of heat related-illnesses are expected to lead to improved forecasts and warnings; and to help shape public safety policy for extreme heat in the Palo Duro Canyon environment.