The National Weather Service declared a heatwave in the Northwestern United States and Pacific Canada on Sunday, June 27. Partly to blame is a weather anomaly known as a "heat dome".Over the past few days, many cities in Washington, Oregon and Northern California, as well as British Columbia, have experienced scorching heat records falling. This includes a reading of 108 F in Seattle (June 27), which was the city's highest ever recorded temperature, and a high of 47 C in Salem (Oregon) on the same day. The power cables melting in the heat caused Portland's streetcar system to suspend service.If you are wondering why we are cancelling service for the day here is what the heat does to our power cables. pic.twitter.com/EqbKUgCJ3KJune 27, 2020 See moreNorth of the Canadian border, Lytton (British Columbia) recorded a high temperature of 116 F (47 C), Monday. This was the highest temperature ever recorded in Canada according to NASA's Earth Observatory.The average summer temperature is increasing each year because of human-induced global warming. Live Science reported that 2020 tied 2016 as the planet's hottest ever year. However, a meteorological anomaly may also be responsible for the heat in the Pacific Northwest. According to CBS News, the heat dome is a combination of high- and low pressure systems that have locked the region in a "mountain of warm air" created by undulations in jet stream (a river eroding high through the upper atmosphere).The jet stream has created a blockage in the atmosphere by trapping a ridge high pressure (that's called the heat dome) above the Pacific Northwest. This blocks the weather system's ability to move on. Instead, the hot air from the high-pressure system presses down on the region, creating an oppressive blanket of heat. According to CBS, these systems are nicknamed "Omega blocks" because of their wind patterns that swirl around the heat block.The National Weather Service reported Tuesday, June 29 that the worst of the weather is over. "The stagnant upper-level pressure over the region [beginning] shift to the east in the next few days." According to the NWS, the highest temperatures are likely to fall in western Idaho, Oregon, and eastern Washington over the next few days. They will eventually shift over Montana on Thursday (July 1st). For large parts of the region, excessive heat advisories are still in effect.Original publication on Live Science
