In the past, we told you about heat waves. Today, we will talk about the opposite phenomenon, which is no less, and possibly even more dangerous.
The Revenant (2015). Twentieth Century Fox Film Corporation
Remember, temperature is simply a measure of how fast the particles within a substance are moving. At higher temperatures, particles move faster, and at lower temperatures, they move slower.
A winter street in Siberian Yakutsk. Photo: Alexei Vasilyev/AP
The temperature changes when objects, that have been heated unequally, meet: the particles with a higher temperature tend to give their energy to the particles with a lower temperature. And this exchange continues to take place until the temperature of the two objects is equalized.
In the Earth’s atmosphere there are air masses — huge masses of air where the temperature is more or less the same. But different masses have different temperatures, and they are constantly exchanging energy, and competing for territory.
The coldest air masses, the polar air masses—during this eternal battle, they sometimes invade closer to the equator, and bring very cold air to places where it is usually warmer. This is the main cause of cold waves—a sudden drop in temperature, that is, within 24 hours, to several degrees below the local seasonal norm.
Exactly how many degrees the temperature has to drop for meteorologists to call it an official cold wave depends on the region: in places with mild winters, it may be 5-8°C in a day, but in climates with habitually cold winters, the value may be much lower.
The regions most affected by cold waves are near polar air masses—Russia, particularly Siberia, as well as Australia, Canada, the northern United States, and the southernmost part of South America.
If we talk about the worst cold waves in the history of observation of weather in the last century, the very worst was the winter of 1941-1942. Then the temperature in Europe, especially in the eastern part, including Moscow, regularly fell to −40 °С.
In our century, one of the worst cold waves is considered to be the sharp cooling in late January 2019 in the northern United States, when the temperature in Chicago fell to −31 °С.
In 2023, Australia was particularly unlucky—in October, a record heat wave was immediately followed by a cold wave: in Sydney, the temperature dropped from 34°C to 14°C in just 2 days. Photo: Bianca De Marchi
Mostly, cold waves occur in the winter months, when it is already cold without them, the happen less often in the fall or the spring. But a sharp drop in temperature, sudden snowfalls, and increased winds can lead to an equally sharp increase in the threat of frostbite and heating disruptions, which not all communities can cope with.
In addition, various equipment and pipes can simply freeze, which at least complicates life, and at the worst can lead to accidents, which are more difficult to avoid in the severe cold.
Paradoxically, cold waves can also lead to more severe fires: because cold air is denser than warm air, which means there is more oxygen in it, which makes combustion more intense.
For these reasons, authorities and meteorologists often warn communities about possible cold waves in advance, so that people have time to prepare—they advise citizens to stay home and dress more warmly if possible, and to keep equipment on so it doesn’t stall or refuse to turn on in extreme conditions.
Text: Jason Bright, a journalist, and a traveler
Cover photo: Kezadri Abdelhak / Unslash
Check out the temperature graph in Windy.app’s EXPERT profile! It shows the possible temperature variations for the upcoming 10 days, which can be useful when you plan your next outdoor adventure!