On Monday, the U.S. National Weather Service (NWS) issued heat alerts that are in effect for 40 million Americans across at least a dozen states, from Montana to Texas and Florida.
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Scorching temperatures will linger in the U.S. Southwest while intensifying in the Midwest this week. A heat dome that has been stationary over the Southwest is expected to stretch into the Midwest.
Temperatures are forecast to reach or exceed 110 degrees Fahrenheit in states including California and Arizona. Arizona's capital Phoenix is on a record stretch of 24 consecutive days with temperatures at or above 110 degrees Fahrenheit.
Meanwhile, severe thunderstorm are forecasted for portions of Connecticut, Massachusetts, New York, Pennsylvania and Vermont.
Thunderstorms will continue to increase in coverage and intensity through Monday as daytime heating destabilizes the atmosphere. The strongest storms will pose a risk of locally damaging wind gusts, according to the NWS Storm Prediction Center.
The world has just sweltered through the hottest June in the 174-year global climate record. The average global surface temperature in June was 1.89 degrees Fahrenheit (1.05 degrees Celcius) above average, ranking June 2023 as Earth's warmest June on record, according to the U.S. National Oceanic and Atmospheric Administration (NOAA).
June 2023 was 0.23 of a degree Fahrenheit (0.13 of a degree Celsius) warmer than the previous record set in June 2020. Last month also marked the 47th consecutive June and the 532nd consecutive month with temperatures above the 20th century average.
Additionally, Earth's ocean surface temperature anomaly -- which indicates how much warmer or cooler temperatures are from the long-term average -- were the highest ever recorded, according to scientists from NOAA's National Centers for Environmental Information.
Climate change and strong El Niño events are behind the unprecedented weather conditions, scientists said.