US and Mexico face ‘heat emergency’

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Nearly 100mn Americans are living in parts of the US that the weather service has flagged as experiencing extreme heat as record-breaking temperatures hit cities across the country.

The heatwave causing the conditions has spread from the lower Midwest to north-eastern states, with temperatures approaching 100F (37.8C).

The US’s National Weather Service (NWS) said the heat would peak in New England, the Ohio Valley and the mid-Atlantic region over the weekend and that “widespread daily record high temperatures” were “likely”.

Several school districts in New York’s suburbs sent students home early because of the heat, while the New York City marathon’s organisers cancelled official training sessions for the race. Michelle Wu, mayor of Boston, declared a three-day “heat emergency” in the city on Wednesday.

The NWS has warned that overnight temperatures will also remain high, meaning those without air conditioning in their homes could find it difficult to cool down.

Climate scientists working with the World Weather Attribution group said heatwaves that hit south-western US, Mexico and Central America earlier this month were made 35-times more likely by climate change.

“Potentially deadly and record-breaking temperatures are occurring more and more frequently in the US, Mexico and Central America due to climate change,” said Izidine Pinto, a researcher at the Royal Netherlands Meteorological Institute who was involved in the study.

The study’s findings “should be taken as another warning that our climate is heating to dangerous levels”, he added.

The dry bed of the lake behind the Santa Catarina dam after high temperatures caused an intense drought in Querétaro state, Mexico © Sandra Hernandez/Reuters

An extreme, prolonged heatwave in Mexico this year caused record temperatures across the country with more than 70 per cent of the nation experiencing drought by the end of May, according to government data.

Dozens of Mexicans have died from heat stroke and dehydration, particularly in the centre and south of the country.

Howler monkeys have been falling from trees after dying of dehydration in Tabasco state, while the reservoirs that supply Mexico City hit record lows, leading to severe water shortages and sporadic protests as the capital experienced its highest-ever temperatures.

The drought has also heightened a dispute over water at the US-Mexico border. The two nations share supplies from the Colorado and Rio Grande rivers following a 1944 treaty, but the drought is complicating Mexico’s ability to fulfil its delivery obligations, angering industries in Texas such as agriculture.

This week Mexico’s extreme weather is forecast to take a different turn, with northern states such as Nuevo Leon expecting up to 25cm of torrential rain — equivalent to more than a third of its annual historic rainfall — due to Tropical Storm Alberto, which made landfall on Wednesday.

Copernicus Climate Change Service, the European earth-observation agency, reported last month that the global average temperature for the past 12 months had risen 1.63C above the pre-industrial average.

The average May temperature of 15.91C was 1.52C above the pre-industrial average, it said, continuing the run of monthly records.