Japan beset by record-breaking heat wave

The big picture: The monthly high temperature records shocked forecasters in Japan and weather record trackers elsewhere.

• Maximiliano Herrera, who keeps tabs on global weather records via social media, has been increasingly struggling to come up with new superlatives to describe extreme weather events. He called the heat wave's intensity "madness" in a post on X.
• According to his data, more than 480 temperature records fell in three days, with the old monthly records broken by more than than 6°C (10.8°F) in some cases.
• "This is the most extreme event in 150 years of Japanese climatic history," Herrera stated.

By the numbers: According to NHK meteorologist Sayaka Mori, 337 high temperature records were broken nationwide during three days, with many of them counting as new monthly highs.

• For example, at Tokyo Haneda Airport on Feb. 19, the high temperature hit 73°F (22.6°C) which was 11.8°C (21.24°F) above average for the date, and a monthly record, Mori stated on X.
• Mori wrote that on Monday, a "shocking" 216 February temperature records were broken in the country, noting that three of these locations have kept weather data since the 1880s.
• In addition, she said, snow depth plummeted to zero at observing sites in Akita, which typically sees heavy snow during the winter.

Between the lines: The unusually mild weather in Japan has disrupted the typical seasonal activities in snowy and cold northern Japan.

• According to Kyodo News, the Kamakura snow hut festival in Yokote was disrupted by rainy conditions and temperatures that climbed well above freezing.
• "This is unprecedented. I hope people don't think this is what Kamakura is supposed to look like," Katsuo Kitajima, a craftsman, told the news organization.

How it works: The proximate cause of the winter warmth was a broad, strong area of high pressure at mid-and-upper levels of the atmosphere and a high pressure area parked to the southeast of Japan.

• The circulation around this high drew warm air from the southwest northward. A colder weather pattern has now returned.
• Numerous studies show that as the planet warms overall, the chances and severity of heat waves — including winter warm spells — are increasing.

• Some recent studies have even found that heat waves would have been "virtually impossible" without human-caused climate change.

The intrigue: The record warmth in Japan matches trends seen in other parts of the world since 2024 began.

• These are likely tied to a strong El Niño event in the tropical Pacific, human-caused global warming, and natural variability, including perturbations in the jet stream that steers weather systems.
• For example, record warmth affected Europe during January into early February, with highs in the low 70s°F in parts of France.
• Record highs were also broken during January in Australia, South America and Asia.

Of note: The Lower 48 states are in the home stretch of what is likely to be one of its warmest winters on record, with temperature anomaly maps dominated by the warmth in the Midwest, Ohio Valley and Northeast.

• Conditions are so unusual in the Midwest, with record low ice extent on the Great Lakes and bare ground where snow cover would normally be, that this winter is being referred to as the "Lost Winter."
• Still more days with above-average temperatures are expected into early March, across much of the country except the West Coast.