Key facts about heatwaves
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The US National Weather Service issued another excessive-heat warning for much of Washington state and Oregon that will remain in effect for the rest of the week. Here is what you need to know about heatwaves:
1 What causes a heatwave?
Heatwaves begin when high pressure in the atmosphere moves in and pushes warm air towards the ground. That air warms up further as it is compressed, and people begin to feel a lot hotter.
The high-pressure system pressing down on the ground expands vertically, forcing other weather systems to change course. It even minimises wind and cloud cover, making the air more stifling. This is also why a heatwave parks itself over an area for several days or longer.
2 What is a heat dome?
As the ground warms, it loses moisture, making it easier to heat up even more. And in the drought-ridden West, there is plenty of heat for the high-pressure system to trap.
As that trapped heat continues to warm, the system acts like a lid on a pot - earning the name "heat dome". In the Pacific Northwest, the heat and the drought are working in concert, exacerbating the problem and breaking temperature records day after day.
3 Why is it hotter than normal in North America?
It has long been known that the world has warmed by more than 1 deg C since 1900, and that the pace of warming has accelerated in recent decades.
The warmer baseline contributes to extreme weather events and helps make periods of extreme heat more frequent, longer and more intense.
4 When will the heatwave end?
Forecasters say temperatures will remain unseasonably hot into next week in the Pacific Northwest.
5 How can I safeguard against possible power outages?
While there have been no major power outages in the Pacific Northwest, the electrical grid could become overloaded with increased energy demands to cool and dehumidify buildings.
To help reduce demand, consider raising the thermostat by a few degrees and closing window shades and blinds. Avoid using large appliances like washing machines and ovens in the hottest part of the day, and turn off all lights and electronic devices not in use. As water heating accounts for about 18 per cent of energy consumed at home, consider shorter or colder showers, the US Energy Department suggests.
NYTIMES
