Record Heat Gives Way to a Stunning 30-Degree Temperature Drop

The last full week of May brought record-breaking heat to much of the East Coast. The unseasonably toasty temperatures were triggered by a strong Bermuda High. What is this atmospheric setup in the Atlantic Ocean, and how does it impact the weather all the way in the U.S.? Read on for all of the details.

East Coast Heat Wave Blamed on the Bermuda High

A large area of high pressure anchored over the Atlantic Ocean was partially responsible for the heat wave that gripped much of the eastern U.S. to start the week. Known as the Bermuda High, this zone of high pressure shifted to the west this week, bringing up warm air from the south and spreading it across the eastern half of the U.S.

Highs skyrocketed into the mid 90s for many of the major metro areas in the Northeast, including Philadelphia and Boston. While the core of the heat was focused on the Northeast, the sweltering conditions reached as far north as New England and as far south as the mid-Atlantic. Over 30 million people in the Northeast and the mid-Atlantic were put under heat alerts as the mercury climbed upwards.

Officials in New York City declared a "Code Red" due to the heat, prompting the city to open hundreds of cooling centers for residents without air conditioning to escape the dangerous conditions. Strain on energy grids was also amplified due to the heat. The U.S. Department of Energy responded by granting the regional grid operator in the mid-Atlantic the power to reduce output to larger energy consumers in an effort to prevent a blackout. Several school districts also dismissed early or went remote for the day to keep students more comfortable.

It is not unusual for the Bermuda High to shape the weather during the summer across the East Coast. It simply exerted its influence a bit earlier this year.

The Bermuda High typically sets up over the North Atlantic Ocean. The area of high pressure is fleeting in nature, often changing positions throughout the year. For instance, the high generally expands westward during the summer and early fall months. This puts it closer to the Bermuda Islands, hence its name. Conversely, the high usually moves farther east in the winter and early spring months. This movement puts it closer to the Azores off the coast of Europe. At this point, the zone takes on the name of the Azores High.

According to the National Oceanic and Atmospheric Administration (NOAA), the Bermuda High moving to the west helps the clockwise winds around the system to pull in the warmer and moisture-rich air from the Gulf of Mexico and Atlantic Ocean farther north. This influx of air is then able to reach the shores of the East Coast, sending both temperatures and humidity levels higher.

The influence of the Bermuda High is most noticeable in the late spring and early summer when the eastern U.S. has not yet acclimated to prolonged periods of warmth. This is why local health officials warn residents to be particularly careful of heat-related illnesses this time of the year.

The unseasonable heat was more pronounced this week after a cooler start to the spring season. Frequent waves of Arctic air diving down from Canada into the U.S. long after winter was officially over kept much of the eastern U.S. under chilly conditions. The persistent intrusions of late-season snow events also delayed the traditional start to the spring.

The Bermuda High is an atmospheric element that forecasters monitor closely during the Atlantic hurricane season. The presence or absence of the high is instrumental in either steering storms toward the U.S. coastline or blocking their advancement.