As most of us are breathing a sigh of relief that 2020 is just about over, many meteorologists are doing the same thing. The year featured devastating wildfires and hurricanes, tornadoes, derechos and flooding, and just about everything else the atmosphere has to offer.

Wildfires and hurricanes were relentless and especially punishing, setting records for the amount of real estate they affected in the Lower 48, while killing dozens. Supercharged by human-caused climate change, they signaled trouble for the future as the climate warms further.

A year filled with extreme weather meant a hefty price tag: Insurance firm Aon estimates that at least 25 separate billion-dollar weather disasters unfolded across the United States this year.

“The United States has endured one of its costliest years for weather disasters on record and is facing an economic toll that will exceed $100 billion,” Steven Bowen, head of catastrophe insight at Aon, wrote in an email.

Fire season

Fueled by record heat and parched vegetation, fanned by howling winds and, at times, sparked by blitzes of lightning, the West was plagued by an onslaught of devastating wildfires that began in June and continued into December.

The fires occurred in a region that is trending hotter, drier and more susceptible to large blazes due to climate change. In California, which saw a record wildfire season, a study published in August showed that the frequency of fall days with extreme fire-weather conditions has already more than doubled since the 1980s.

In early September, when fires exploded amid howling land-to-sea winds not only in California but also Oregon and Washington, Nick Nauslar, a meteorologist at the National Interagency Fire Center in Boise, Idaho, said the eruption surpassed anything in the modern record.

“Multiple fires made 20+ mile runs in 24-hours over the last few days in California, Oregon, and Washington,” he said in an email. “Most of these fires are making massive runs in timber and burning tens of thousands of acres and in some cases 100,000+ acres in one day. The shear amount of fire on the landscape is surreal, and no one I have talked to can remember anything like it.”

In mid-September, the smoke from these blazes led to hazardous levels of air pollution all along the West Coast and covered almost the entirety of the Lower 48, even reaching D.C.

Colorado also experienced record wildfire activity this fall that was only finally quelled when snow arrived.

California fires

The 2020 wildfire season in California was off the charts in terms of area burned. Some 4.2 million acres were torched in blazes in just the Golden State alone. That’s an area larger than Connecticut and twice as extensive as what burned in California’s previous worst fire season.

Thirty-one people died in California wildfires, which damaged or destroyed more than 10,000 structures. Five of the top six largest wildfires in the state all occurred in 2020.

The first big eruption of fires came in mid-August as a record-breaking heat dome smothered the Southwest. Death Valley soared to 130 degrees Fahrenheit, potentially Earth’s highest temperature since at least 1931. The fires that erupted in Southern California exhibited extreme fire behavior, spreading at breakneck speed.

Some of the smoke plumes towered more than 50,000 feet high, taking on thunderstorm characteristics. A family of virtually unheard-of fire tornadoes — actual tornadoes made out of smoke and borne of fire — descended from roiling smoke clouds in Lassen County, Calif., on Aug. 15. The Creek Fire in the southern Sierra Nevada in September spun up additional tornadoes.

Another rash of blazes broke out Labor Day weekend in the central and northern part of the state, including over parts of its famed wine country in Napa and Sonoma counties.

By mid-September, San Francisco was bathed in an eerie, apocalyptic amber hue beneath dense plumes of smoke pooling over the Bay Area that took weeks to fully disperse.

The fire season in California extended into December, when the Weather Service office in San Francisco issued a red-flag warning for the possibility of extreme fire behavior for one of only a few instances on a record so late in the year.

Oregon and Washington fires

Wildfire disaster struck the Pacific Northwest in September amid howling, dry winds. In Washington state, fires charred 600,000 acres, the largest burned area since 2015.

In Oregon, blazes consumed more than a million acres and burned down 4,009 homes, according to the Statesman Journal. At one point, more than 10 percent of the state’s population was under an evacuation warning or order.

Colorado fires

Colorado saw its three largest fires on record occur in 2020. First came the Pine Gulch fire in late July north of Grand Junction, which scorched nearly 140,000 acres. The Cameron Peak Blaze, which began in August west of Fort Collins, was the largest of the three, burning 208,000 acres over four months. Then came the East Troublesome, which torched 192,560 acres in October, at one point growing 100,000 acres in less than 24 hours. The fire burned through parts of the popular Rocky Mountain National Park, and became one of the few blazes on record to jump the continental divide by blowing embers across a two-mile treeless stretch.

Not until a snowstorm arrived at the end of October were the Cameron Peak and East Troublesome fires finally contained.

The fires raged amid a severe drought, aggravated by record heat, through stands of trees killed or weakened by years of a bark beetle infestation. Each of these trends are tied to climate change, which is tilting the odds in favor of larger and more destructive fires in the West.

Hurricane season

Hurricane Season 2020 will be remembered for decades to come. It proved the busiest Atlantic hurricane season on record with 30 named storms, more than two-and-a-half times the seasonal average.

Thirteen hurricanes and six major hurricanes punctuated an unending meteorological assembly line. A record 12 named Atlantic storms made landfall in the Lower 48, including five in Louisiana. Two of those landfalls, Laura and Delta, were within 15 miles of each other, and both ravaged the Lake Charles area.

Ominously, 10 storms rapidly intensified, their peak winds strengthening by at least 35 mph in 24 hours, tying 1995 for the most in a single season. Studies have shown rapid intensification becoming more likely as ocean waters warm due to climate change.

Tropical systems caused at least $38 billion in damage across the Lower 48.

Isaias

Hurricane Isaias wasn’t an overly intense storm, having peaked only at Category 1 strength, but it will be remembered for the Mid-Atlantic tornado outbreak it produced, heavy rainfall and a large number of power outages in New England. Its swath of damaging winds covered highly populated real estate from North Carolina to New York City.

The system spawned some 39 tornadoes as it rolled up the Eastern Seaboard, including a 145 mph EF3 that killed two in Bertie County, S.C. It proved the strongest tropical-cyclone-generated tornado in the United States since 2005. Tornadoes also struck Dover, Del., and near Philadelphia, the swarm especially intense on the Delmarva Peninsula.

Strong winds from the Carolinas to southern New England resulted in 3.6 million customers without power. Con Edison, the utility serving New York City, reported the second-most outages in company history, behind Hurricane Sandy in 2012.

Laura and Delta

Hurricane Laura formed in mid-August, but it stayed weak at first, only achieving hurricane strength on Aug. 25 when it reached the Gulf of Mexico. The storm rapidly intensified into a major hurricane, eventually reaching peak intensity as a high-end Category 4 before landfall in southwest Louisiana on Aug. 27.

Laura caused severe damage to Lake Charles, home to more than 75,000 people. It swept ashore a 17-foot storm surge at the coast, brought gusts to 150 mph and caused tornado-strength wind damage to a 30-mile-wide swath of Interstate 10.

One-and-a-half million people were evacuated in advance of the storm, which was one of the strongest on record to make landfall in the United States. It was also the first major hurricane in a season that had previously featured only tropical and Category 1 storms.

The same area was hit by Category 2 Hurricane Delta during the second week of October, a storm that brought 100 mph winds and a nine-foot storm surge. The hurricane unloaded at least five inches of rain on 3.5 million people in Louisiana and surrounding states.

Hurricane Sally

Sally formed Sept. 11 from a tropical wave east of the Bahamas. It slowly meandered west and clipped the southern Florida Peninsula before becoming a hurricane. It drifted shoreward at only 2 mph, nearing the Alabama coastline the night of Sept. 15-16. The storm simultaneously rapidly intensified, making landfall near Gulf Shores as a 105 mph high-end Category 2.

Sally dropped up to 30 inches of rain, yielding historic flooding while also spurring widespread moderate wind damage. A section of the Pensacola Bay Bridge collapsed in the turbulent seas, which accompanied a three-to-six-foot storm surge in spots. Sally was the first hurricane to make landfall in Alabama since Ivan in 2004.

Thunderstorms and tornadoes

While hurricanes and wildfires were unforgiving, thunderstorms and tornadoes were the most expensive disasters in the Lower 48 in 2020.

Fourteen of the 25 billion-dollar weather disasters in 2020, headlined by the Iowa derecho in August and Nashville tornado in March, were from severe thunderstorms.

“Perhaps to the surprise of many people, the biggest driver of losses in 2020 came from severe convective storms,” Bowen said.

Iowa derecho

On Aug. 10, a cluster of run-of-the-mill thunderstorms in eastern Nebraska defied forecasts, exploding into an arcing squall line of extremely destructive straight-line winds known as a derecho. The storms blasted through Iowa with 140 mph wind gusts, buffeting 43 percent of the state’s corn crop and wreaking widespread havoc. Cedar Rapids was hit particularly hard, with numerous homes and businesses destroyed, and only a fraction of trees left standing.

Damage rivaled that of an EF2 or EF3 tornado, but in a swath some 75 miles wide. Power outages lasted for weeks.

The storms barreled east into Chicago, with embedded tornadoes and winds estimated near 80 mph. In the derecho’s wake lay $7.5 billion in damage, making it the single costliest thunderstorm event in U.S. history.

The Iowa derecho was just one of several such destructive storm complexes to rake across portions of the Lower 48. A derecho slammed Philadelphia and southeast New Jersey in early June. Another derecho blasted a zone from Utah to Nebraska, including Denver, just a few days later.

Nashville tornado

At least two dozen died following a pair of surprise tornadoes that carved through middle Tennessee overnight March 2 into March 3, striking the downtown Nashville area before cutting a strip through the landscape farther to the east over the next 50-plus miles. The tragedy was tied to a lack of timely warnings and advanced preparation, the forecasts indicating only a “marginal” risk for any severe weather, as the tornado threat initially appeared low.

The first tornado, which touched down around 12:35 a.m. that Tuesday just west of Nashville, demolished most of the John C. Tune Airport. The voracious vortex then roared through the heart of Nashville, passing just north of the state capitol and tossing debris 20,000 feet high.

The tornado was on the ground for more than 50 miles before finally lifting nearly an hour later. Shortly thereafter, an even stronger EF4 tornado touched down near Cookeville, Tenn. around 2 a.m., killing at least 18.

Mississippi tornadoes

At least 351 tornadoes were tallied across the Lower 48 in April, marking the deadliest month for tornadoes since 2013 and the second most active April on record. April brought the year’s tornado fatality count to 73.

Three outbreaks punctuated the month, including one on Easter Sunday that produced at least 150 tornadoes. It proved the third most prolific tornado day on record as swarms of twisters marched across the South.

Among them were a pair of wedge tornadoes that stampeded across southern Mississippi north of Hattiesburg, leveling large chunks of Bassfield, Soso, Laurel and Moss. One was rated a 190 mph EF4, a buzz saw of wind that peaked at 2.25 miles wide. That proved the widest tornado in Mississippi state history and the third largest ever to touch down in the United States. The tornado was sufficiently large to virtually swallow Bassfield.

Just a half-hour after the tornado’s monstrous rampage, a mile-wide EF3 developed to the north. The twin tempests killed a dozen and prompted “tornado emergencies,” the most dire type of alert issued by the National Weather Service.

Winter storms

The year began with a rather tame winter, as a stable polar vortex kept blasts of frigid air bottled up that might otherwise trigger major snowstorms in the Lower 48 states.

But the winter of 2020-2021 started with a blast, as a blockbuster snowstorm charged up the Mid-Atlantic and Northeast coasts.

December nor’easter

A seemingly unremarkable wave of low pressure drifting south of New England on Dec. 16 and 17 led to one of the most prolific Northeast snowstorms in recorded history. A dumping of 35 to 45 inches of snow in 24 hours occurred in 350-mile band stretching from northern Pennsylvania and New York state, through Vermont and New Hampshire, and into western Maine.

Pennsylvania may have set a new state record for 24 hours’ snowfall — 43.3 inches in Alba, a small town in the north-central part of the Keystone State. State snowfall records may have also been challenged in Vermont and New Hampshire, where totals also topped 40 inches.

In Binghamton, N.Y., 41 inches came down in 18 hours.

Andrew Freedman contributed to this report.