Assessing NWS Pendleton heat criteria, response, and adaptation in eastern Oregon

Heat waves have been shown to have significant human health impacts, particularly for vulnerable populations such as older adults. Heat waves are expected to increase in both intensity and duration with global climate change (Clark et al. 2006; Meehl and Tebaldi 2004). Places that typically experience a moderate climate, such as Oregon, may have greater negative impacts associated with heat waves as they are not as acclimated to extreme heat and long duration heat waves. The Oregon Health Authority (OHA) examined the relationship between heat and illness in order to determine what constitutes a heat event of public health significance in Oregon.

We analyzed zip code level weather station and health outcome data during the warm season (May-September) for the years 2000-2009. Poisson regression was used to model numerous daily hospitalization and mortality outcome counts versus daily temperature variables at the zip code level while controlling for temporal trends and potentially confounding factors.

Daily maximum temperature was consistently the strongest climatic predictor of health outcomes. We found that adults 65 and older had a slightly higher risk for heat-related illnesses. There were also major regional differences in risk. For example, the Oregon coast was the most vulnerable to high temperatures. Over the 10-year study period there were 333 documented hospital admissions for heat-related illness and 18 documented heat stroke deaths. Increases in daily maximum temperature were significantly associated with rates of hospitalization for heat-related illness, electrolyte imbalance, nephritis, kidney failure, and near drowning, as well as with rates of death due to heat stroke and drowning.

Despite its mild, ocean-moderated climate, Oregon does experience instances of extreme heat. The most recent significant heat wave in the Pacific Northwest in late July 2009 shattered single station records and was impressive in terms of magnitude of the daytime temperatures and length of the event in terms of elevated nighttime temperatures (Bumbaco et al., in review). Daily high temperatures were significantly and consistently associated with several hospitalization and mortality outcomes. The following thresholds were established at temperatures where we observed sharp increases in risk: Statewide, 100°F; Coast, 90°F; Willamette Valley, 100°F; Central/Eastern, 100°F; Southwest, 105°F. However, older adults are more vulnerable and may experience heat-related illness at lower temperatures, depending on their health status. These results will be used to reassess the criteria for issuing heat advisories and to improve heat response by Oregon health agencies.

In 2010, the State of Oregon Climate Adaptation Framework identified an increase in extreme heat events as a climate risk for which the state must plan. This risk was identified because of the magnitude of the recent 2009 event, the literature suggesting that heat waves will increase, thereby exacerbating the relative vulnerability of the Pacific Northwest. The charge of the framework was for state agencies to implement short-term, low-cost actions to help build resiliency from climate impacts in the state of Oregon. The Oregon Climate Change Research Institute (OCCRI) worked with the Oregon State Agencies to identify climate risks, and is now collaborating with the Oregon Health Authority (OHA) to begin to discuss measures for implementing this piece of the framework. It was determined that the National Weather Service (NWS), which issues weather-related warnings, and has high visibility, would be a logical partner in this endeavor. Armed with the findings of the OHA study, OCCRI serves as a liaison in this effort, connecting the state agency to the National Weather Service. The OHA-OCCRI-NWS partnership strives to evaluate the early warning systems in place by the NWS, while connecting the OHA health research to climate science in the Pacific Northwest.

NOAA's National Weather Service (NWS) issues various heat products to inform and warn the public of expected or imminent excessive heat events.  To determine warning criteria for large metropolitan areas, the NWS employs a methodology that uses meteorological data and large city demographics to calculate variations in human mortality due to excessive heat.  To determine criteria for areas other than large cities, the NWS takes into account the Heat Index and information such as: time of year, humidity, and number of consecutive hot days.  The NWS could improve criteria for these areas by considering additional information, such as morbidity, thereby making the heat products more useful to decision makers.  Using results from heat-health studies conducted by the Oregon Health Authority and the Oregon Climate Change Research Institute could be an efficient way to help the NWS improve excessive heat products. In this pilot, we study the heat-related practices of the Pendleton, OR office. The Pendleton Weather Forecast Office covers the inland areas of Oregon and Washington, where temperatures over 100˚F are more frequent than west of the Cascade Mountain Range.