The dramatic weather extremes of summer 2021 are demonstrated in these images that meteorologists use to understand the atmosphere.
An off-the-scale deluge in New York
Tragedy struck densely populated sections of the Northeast on Sept. 1 as the remnants of Ida, once a Category 4 hurricane, interacted with a warm front over New York.
The storm dumped up to a foot of rainfall, with rates locally exceeding four inches per hour, on soils saturated by Tropical Storm Henri’s moisture just a week before. The torrent led to a catastrophic round of flash flooding that swept away cars and engulfed basement apartments.
This image from a forecast tool called MRMS-FLASH shows where flash flooding may occur via a metric known as unit streamflow, which approximates runoff. White pixels, representing off-the-scale value of this metric, cover a wide swath of the New York metropolitan area.
Off-the-chart heat anomalies in the Pacific Northwest
Abnormally high pressure, very dry soil, sinking air from nearby mountains and climate-change-induced warming combined for one of the most exceptional meteorological events in modern history in the Pacific Northwest during late June.
Temperatures 30 to 50 degrees above average resulted in all-time record heat in almost every location in the region. Some locations shattered these all-time marks by 10 degrees. Seattle doubled the number of times it has hit 100 degrees, and Canada’s all-time heat record was broken three days in a row.
The image below shows the enormous area with temperatures at least 18 degrees (and up to 42 degrees) above normal from June 29 to 30.
A blanket of smoke
As in many previous years, this summer featured a disastrous outbreak of wildfires that were intensified by the hot, dry conditions in the western United States. This included the Dixie Fire, the second-largest wildfire on record in California.
As the fires burned massive amounts of plant debris, the jet stream transported a dense blanket of smoke east over much of the country. This simulation shows the smoke’s reach in late July, when it blotted skies red and diminished air quality as far east as New York and Washington.
The devastating hurricane that would not quit
When Hurricane Ida made landfall in southeastern Louisiana on Aug. 29, it brought some of the Gulf of Mexico with it. A tremendous storm surge, or rise in ocean water above normally dry land, pushed north through millions of acres of low-lying marshland, allowing the storm to sustain strength for hours even after moving inland.
This satellite image shows Ida five hours after landfall, still hosting a remarkably intact core and unmistakable eye surrounded by a ring of intense thunderstorms.
A disastrous swath of rainfall
August 2021 was the deadliest month for flash flooding in the United States since Hurricane Harvey submerged Houston in August 2017. It was in large part due to a calamitous heavy rain event on the 21st that sent torrents of water raging through middle Tennessee.
Meteorologists often speak of very heavy rain events in terms of recurrence interval, or the average number of years we would expect to have to wait between two events of a certain magnitude. For a swath of middle Tennessee, the recurrence interval exceeded 200 years, maxing out the scale.
Hottest summer on record for the Lower 48 states
Some weather records are so unbelievable that they feel unapproachable; for example, the heat in the summer of 1936. That summer, amid the drought marking the Dust Bowl, an intense dome of high pressure over the middle of the nation forced weeks of unprecedented heat. It was easily the warmest summer on record at the time, and it held through recent decades despite human-caused global warming.
But the persistent heat this summer managed to edge past the 1936 numbers. This image shows just how pervasive record-setting and much-above-average temperatures were in 2021.
Feuerstein is a college junior studying meteorology at Cornell University.