The situation is greatly amplified by increasing background temperatures due to the burning fossil fuels. “When the land surface is drier, it can’t cool itself through evaporation which makes the surface even hotter, which strengthens the blocking high further,” she said in an interview. Jane Wilson Baldwin, a postdoctoral researcher at the Lamont-Doherty Earth Observatory at Columbia University, said that given the severe drought in the West right now, many feedbacks between the land and the atmosphere are combining to produce an unusually persistent extreme. With very little moisture in soils right now, heat energy that would normally be used on evaporation - a cooling process - is instead directly heating the air and ground surface. The high summer sun angle combined with those cloudless skies then in turn further heats the surface.īut the vicious feedback loop doesn’t end there: the combination of heat and drought is working to send this heat wave into truly extreme territory. That is translating into scorching temperatures for inland areas and deserts.Īs the ground warms, it loses moisture, which makes it easier to heat even more.Īs a high-pressure system becomes firmly established, subsiding air beneath it heats the atmosphere and dissipates cloud cover. A weather balloon in San Diego measured a record temperature of 89.2 degrees in the lower atmosphere on Thursday, which Tardy called a “very significant” reading for this location and time of year. For this pressure level to stretch to heights of 600 dekameters, or 19,685 feet, is quite rare, but that marker was forecast for this week, and it was indeed reached in Flagstaff, Ariz., on Tuesday.Īlex Tardy, a meteorologist with the National Weather Service in San Diego, noted in an email that what is unusual about this particular heat dome is its strength and size, and the fact that it is only mid-June. One way to gauge the magnitude of a heat wave is to measure the height of the typical halfway point of the atmosphere - at the 500 millibar pressure level. Hot air masses expand vertically into the atmosphere, creating a dome of high pressure that diverts weather systems around them. On Wednesday, Las Vegas soared to 116 degrees, one shy of its highest temperature ever recorded, while Grand Junction, Colo., hit 105, matching its highest temperature ever observed in June. Salt Lake City, Sheridan and Laramie, Wyo., and Billings, Mont., all made history, soaring to 107, 107, 94 and 108 degrees, respectively. This flurry of heat-dome-driven records follows temperatures that matched all-time highs on Tuesday in parts of Utah, Wyoming and Montana. Texas is pushing homes and businesses to conserve electricity for a second day in a row to stave off blackouts. People wait in line for snow cones during a heat wave in Dallas on Thursday. Omaha set a daily record high of 105 degrees, its hottest June day since 1953 and its third highest June temperature.Sacramento set a daily record high of 109 degrees, shattering the previous record of 102.It also set a daily record high of 114 degrees. Las Vegas’s low temperature of 90 degrees was its warmest on record so early in the season.Tucson reached at least 110 degrees for a sixth straight day, tied for the longest streak on record.“Denver’s climate record goes back 150 years.” “ll of the 100☏ streaks in Denver history lasting three or more days have occurred in the past 32 years,” tweeted Bob Henson, a meteorologist and weather journalist.
Denver reached at least 100 degrees for the third straight day, the earliest occurrence of such a streak on record.“Only 18 other days in Phoenix’s period of record have reached 118° or greater,” tweeted the National Weather Service office in Phoenix. Phoenix hit 118 degrees, a record for the date, and the earliest the city has observed a temperature this high.Death Valley, Calif., hit 128 degrees, the highest temperature measured anywhere on the planet so far this year and just one degree off its June record of 129 set on the 30th in 2013.Palm Springs, Calif., matched its highest temperature ever recorded, soaring to 123 degrees.This lengthy list of temperature records on Thursday, from California to Nebraska and far from comprehensive, is a testament to this heat dome’s might: Source:, University of Maine, Climate Change Institute