The United States continues to suffer extreme weather as a heatwave baked millions across the upper midwest and north-east and a tropical storm soaked Texas and northern Mexico.

The National Weather Service said the heatwave was expected to peak in the eastern Great Lakes, New England, the Ohio Valley and mid-Atlantic over the coming weekend.

“Widespread daily record high temperatures are likely. Heavy to excessive rainfall will be associated with thunderstorms forecast to move across parts of the northern Plains and Upper Midwest,” it said in a weather advisory on Thursday.

A tropical cyclone building in the Gulf of Mexico named Alberto is forecast to bring heavy rain, flooding threats and gusty winds to south Texas but “gradually decrease” as it makes landfall in Mexico and dissipates.

An air-quality alert was issued for New York City where an early season heatwave continues to tax residents. Highs are expected to reach 92F (33C) on Thursday, while RealFeels will surge to nearly 100F (38C). Conditions are expected to ease over the weekend.

In New Mexico, where a wildfire tore through the village of Ruidoso in the southern part of the state on Tuesday, killing two and destroying 1,400 buildings, Governor Michelle Lujan Grisham has asked the White House to declare two fires a major disaster.

In Caribou, Maine, which has become a meteorological place of interest given its northerly US location, high temperatures records were tied on Wednesday to a record set in 2020 when the thermometer reached 96F.

In Bangor, Maine, Wednesday’s high of 95F tied the record which was last set in 1995. The all-time high temperature record in Bangor is 104F, set on 19 August 1935.

The soaring temperatures are attributed to meandering fluctuations in the jet stream that can allow heat domes, or persistent regions of high-pressure over an area.

“When these meanders in the jet stream become bigger, they move slower and can become stationary. That’s when heat domes can occur,” explains William Gallus, a professor of meteorology at Iowa State University.

Historically, heat domes have been blamed for a record 739 deaths over five days in Chicago in 1995; the US southern plains heatwave of 1980 when 10,000 people died; for record temperatures in Phoenix, Arizona, last summer; and for the US Dust Bowl in the 1930s.

Brett Anderson, a climate expert and senior meteorologist with AccuWeather, said in an email that a massive and persistent ridge of high pressure in the atmosphere has been covering much of Mexico since early March.

“This has basically prevented most cold fronts from reaching the northern part of the country during the spring, which has allowed tremendous amounts of heat to build up over the past three months. During June, this pocket of heat began to expand northward into the Southwest US,” Anderson wrote.

The high pressure, he added, had “greatly limited shower and thunderstorm activity, by redirecting most of the tropical moisture away from the country, leading to unusually dry conditions and severe drought”.

Anderson said that “climate change is clearly playing a role in enhancing this warming. We are also coming off a moderate to strong El Niño. This is usually the time period, the later stages of El Niño, that we see the greatest warming influence from this natural phenomena.”

But El Niño is typically followed by La Niña that typically has a slight cooling influence on the average global temperature. However, he wrote: “Global temperatures for 2025 will still likely rank in the top ten hottest years on record due to global warming.”

Source: theguardian.com