Buzz
If you’ve been feeling like this summer is unusually hot, you’re correct. According to the National Oceanic and Atmospheric Administration (NOAA), Earth saw its hottest recorded days during the week of July 2–8, 2023, with global average temperatures hitting 17.18°C (62.92°F). In the southwestern United States, a relentless heat dome is causing record-breaking highs in regions already accustomed to extreme heat. Phoenix, Arizona, could surpass its 1974 record of 18 consecutive days with temperatures over 110°F; meanwhile, the combined heat and humidity in Houston and other Texas cities in June led to a heat index of 125°F.
Simply put, a heat dome happens when warm oceanic air is trapped in Earth’s atmosphere by a high-pressure system. In years like 2023, when either El Niño or La Niña warms the western Pacific, hot air accumulates over the ocean and spreads eastward across the land. The high-pressure “dome” holds the hot air in place, causing it to sink toward the ground. This trap prevents the heat from escaping, thus intensifying the temperatures.
While heat domes are not uncommon, some can be especially intense and result in significant challenges.
In 2021, the usually cool Pacific Northwest endured weeks of extreme heat due to a heat dome. Cities in Washington and Oregon broke triple-digit temperature records, exceeding 110°F. The intense heat overwhelmed hospitals with weather-related emergencies and led to the deaths of more than 60 individuals.
Heat domes can also trigger wildfires and harm marine ecosystems. The 2021 heat dome in western Canada caused the deaths of over a billion marine animals along the Pacific coast, according to the Guardian.
A 2021 study published in the journal Nature Climate Change [PDF] forecasts that climate change will intensify both the frequency and severity of extreme heat events. It might be wise to invest in a quality (energy-efficient) air conditioner, as more heat domes are likely to occur in the future.
This article was first published in 2021 and has been updated for 2023.
