PNW reflects on anniversary of historic Heat Dome as summer weather kicks off

As the song went from Disney’s Little Mermaid movie, it was Hot, Hot, Hot! Look out for similar temperatures on June 25 through 28.

It has been four years this week since the historic ‘heat dome’ parked over the Pacific Northwest during the last week of June, surging temperatures well past all-time highs.

What is a Heat Dome?

A ‘heat dome’ is a strong high-pressure system aloft that gets cut off from the main westerly flow around the Northern Hemisphere, in this case across the Northern Pacific Ocean. The system’s sinking air motion and resulting low-level offshore flow toward the ocean produced the blistering temperatures.

As an analogy, think of this upper-level high-pressure system as a large rock in a river, resting in one spot while the water flows around it.

The descending air in a heat dome over time creates a warmer and warmer air mass. Between June 25 and 28, 2021, temperatures in the region warmed each day, peaking on the 28th, crushing previous all-time highs.

Bellingham soared to 99 degrees, Everett Paine Field 100, Arlington 103, SeaTac Airport 109, Olympia and Forks 110, and Portland, Oregon, a sizzling 116 degrees. The hottest temperature in the state was a scorching 120 degrees at Hanford near the Tri-Cities.

Heat wave impacts

During this historic heat wave, more than 250 people in the Pacific Northwest succumbed to the heat, and in Western Canada, over 400 people perished. Extreme heat is the No. 1 weather-related hazard yielding fatalities in the world. It kills more people than all other weather-related hazards like hurricanes, floods, tornadoes, and winter storms combined.

Yet with the ongoing warming of the planet, the global upper-level air pattern has been tending to produce more of these cut-off upper-level high-pressure systems, which create extreme heat waves. For instance, much of the middle and eastern parts of the U.S. are suffering through a heat wave early this week.

Last year, heat waves were felt not only in the United States but also in Europe, Japan, India, Southeast Asia, and Pakistan. Temperatures in India and Pakistan soared to around 125 degrees.

Can a Heat Dome happen again in the PNW?

The latest seasonal summer weather outlook for Western Washington reflected good odds on warmer average temperatures into September and at or below normal precipitation during the driest time of the year.

With the ongoing warming of the planet, intense heat events in the Pacific Northwest can no longer be ruled out. The odds of another heat dome this summer or in the coming years are similar to rolling snake eyes 3 times in a row. Yet, it could happen again.

What to do if it gets hot:

If sensitive to excessive heat, here are some precautions to help during a period of hot weather.

• Be sure to stay hydrated and drink plenty of water.
• Spend time in an air-conditioned location to help relieve the stress of the heat.
• If outdoors, seek shade and use sunscreen to avoid a sunburn.
• During the heat of the day, avoid strenuous activities like running.
• If working outdoors, take breaks in shade and drink plenty of water.
• Avoid leaving children and pets in cars, even for just a few minutes, with the windows open.
• Wear light, loose-fitting clothing to help reflect heat.
• If on area waterways, be sure to wear a properly fitted life jacket to avoid falling into the cold water and suffering cold water shock, and drowning.
• For meals, eat easy-to-digest foods like salads and fruit.

Be sure to check on elderly family members, friends, or neighbors to help ensure they are doing okay during hot weather, particularly if they take medications. Studies have revealed that common treatments such as heart medicines, antihistamines, and decongestants don’t mix well with heat. Continue to take the medications, just stay cool, and stay hydrated. Consult with a doctor for any concerns.

Always monitor the latest weather forecasts for the potential of any heat waves. The National Weather Service has a publicly available heat-related resource called HeatRisk. This resource is a color-numeric index that shows a forecast threat of heat-related impacts.

HeatRisk takes into consideration how unusual the heat is for the time of year, the days of the expected hot weather, including not only daytime temperatures, but also temperatures overnight, and the elevated risk of heat-related health impacts.

HeatRisk was tested in the Western U.S. for a number of recent years, including the Seattle Forecast Office, and has been expanded nationwide. The resource has been quite useful during the heat wave across much of the eastern two-thirds of the country. Many TV weather segments have placed the colorful heat graphics on screen, highlighting areas of risk.

Enjoy this summer; just do so safely, particularly during periods of hot weather.

Ted Buehner is the KIRO Newsradio meteorologist. You can read more of Ted’s stories here and follow him on X.