Thanks in part to the epic heat wave that sent temperatures skyrocketing in the Southwest, last month was the hottest June on record for the contiguous U.S., the National Oceanic and Atmospheric Administration announced Thursday. June was 3.3°F above the 20th century average of 68.5°F, beating the previous record set in 1933 by 0.2°F, according to
MoreMost of the U.S. should get ready for some serious summer weather next week. Searing temperatures — and in some places high humidity — will reign thanks to a large ridge of high pressure that’s expected to set up camp over the Lower 48.
While forecasters say it is too early right now to pin down the details of where the epicenter of the worst heat and moisture will be, the focus looks to be in the central U.S.
Such heat waves are fairly typical for this time of year, and many parts of the country see their highest temperatures in July. But as the world warms from global warming, such heat waves are expected to become more intense and happen more often.
‘Normal,’ But Still Hot
The ridge is the result of the overriding pattern of atmospheric flow over the country that will help push hot air northward next week, all the way up to the Canadian border in the central U.S.
Temperatures will reach highs in the 90s and over 100°F (37.8°C) depending on the location. In areas that will see a northward surge of Gulf moisture — particularly the Southeast and the central states — the heat indices could be well above 100°F.
The forecast heat index across the country for Thursday, July 21.
The exact details are still in play this far in advance but the overall pattern is “pretty well locked in,” Richard Bann, a meteorologist with the National Weather Service’s Weather Prediction Center, said.
No widespread record highs are expected, but that “doesn’t take away from the fact that it is hot,” he said.
“As of now, I’d say we’re due for a ‘normal’ summer heat wave that we often see in the Southern Plains,” Gary McManus, the Oklahoma state climatologist said in an email.
The plains states are watching to see if the heat has any potential impacts on soil moisture, as sustained high heat can lead to flash drought in the region. But “a good dose of moisture” in recent days should help alleviate some of the drought that had begun to develop and could protect against the heat next week, McManus said.
In the Southeast and Northeast where drought has developed and worsened this summer, the heat could further exacerbate conditions. In the Southeast, that will depend on whether any rains come to help offset the heat, said David Miskus, a senior meteorologist with the Climate Prediction Center at the National Oceanic and Atmospheric Administration.
The exceptions to the heat will be the Pacific Northwest, which is expected to see a cool down thanks to a low pressure system working its way southward along the west coast of Canada, and northern Alaska, which will see temperatures drop after record-breaking heat this week.
The North Slope town of Deadhorse recorded a high temperature of 85°F (29.4°C) on Wednesday, a record for the area. Climatologist Brian Brettschneider said it was the highest temperature recorded within 50 miles of the Arctic coast of Alaska. (Deadhorse is 10 miles from the sea.) While it may not sound hot to residents of Atlanta or Houston, normal July high temperatures in Deadhorse are only in the 50s, Bob Henson at Weather Underground reported.
The other major heat wave in the U.S. so far this summer was the one that sent temperatures soaring across the Southwest in latter part of June. That event helped make the month the hottest June on record for the contiguous U.S.
Heating Up
As the Earth’s temperature continues to rise thanks to the unrelenting buildup of heat-trapping greenhouse gases in the atmosphere, heat waves are likely to become more intense and happen more often across the U.S. and the planet as a whole. That projection is one of the most solid of climate science. Scientists have even found that some recent heat waves were made more likely by warming.
How global warming will shift the odds in favor of more extreme heat.
Recent studies have put an even finer point on the matter. A February study in the journal Climatic Change suggested that the worst of the worst heat waves — ones that happen about once every 20 years now — could become an annual threat by 2075 for parts of the world, including parts of North America.
Humidity can compound the potential ill effects of heat waves, particularly in vulnerable populations like the very young, the elderly and those with underlying medical conditions. High humidity stymies the body’s natural heat defense system, perspiration.
Another recent study suggested that in some regions, including several that are expected to see the highest population growth in the coming decades, future heat waves could see a combination of sky-high temperatures and oppressive humidity that could reach the theoretical limit of what a healthy human body can cope with.
Research by Climate Central has also showed that there will be an increase in “danger days” with high temperatures and humidity across many cities in the U.S. The three states expected to see the biggest increases in such days are Texas, Florida and Arizona.
