Temperatures in parts of the western United States may reach 110F (43C) on Sunday. A widespread and significant heat wave is forecast to bring oppressive conditions to drought-affected western states over the weekend, with the possibility of all-time records being broken, according to the National Weather Service on Friday. A developing heat dome will extend from northwestern states into the northern Plains. Extremely hot daytime temperatures combined with potentially record-warm overnight lows will increase heat stress, resulting in widespread major to locally extreme HeatRisk, the agency stated. The highest level on the HeatRisk scale can affect anyone lacking cooling or hydration, and energy grids are likely to face strain. A science fellow at the Union of Concerned Scientists noted that the heat wave is occurring in a fundamentally different system influenced by human-caused climate change. Marine heat waves in every ocean basin are releasing substantial heat into the atmosphere, affecting weather patterns worldwide. A developing super El Niño in the equatorial Pacific may also contribute to the heat dome. Sea surface temperatures in the central Pacific are warming rapidly, altering storm energy patterns that influence the jet stream and allow the heat dome to form over the western United States. This event follows similar heat waves that affected the central and eastern United States last week and Europe earlier. An analysis by the World Weather Attribution group indicated that the recent hot and humid conditions in the United States would have been virtually impossible without human-caused climate change. Hot and windy conditions will raise wildfire risks, as much of the western United States is already abnormally dry or in drought. Heat domes can produce dry thunderstorms where rain evaporates before reaching the ground, and lightning may ignite fires. A National Interagency Fire Center map shows elevated risk in Washington, Oregon, Idaho, Montana and Wyoming.
