2021 was Boston’s warmest year on record

Donald Calway listened to his car radio while soaking in the sun on William J. Day Boulevard in Boston, Mass., on July 31, 2019.Craig F. Walker/Globe Staff

Boston may be chilly today, but it just wrapped up its warmest year in recorded history. In 2021, the average temperature at Logan Airport was 52.4 degrees Fahrenheit, according to the National Weather Service’s Boston bureau. That’s .2 degrees warmer than the previous record set in 2012.

The news doesn’t come as a big shock, since Boston has been breaking temperature records all year. The city saw above-average temperatures in all but three months of 2021. It had its warmest winter, third warmest autumn, and hottest summer on record. The city also failed to set a single low-temperature record in 2021, instead seeing nine days where low temperatures were the warmest they’ve been on that day since the start of the historical record in 1872, according to the Northeast Regional Climate Center.

Although temperatures can vary from year to year, there has been a clear upward trend amid the climate crisis.

“Seven out of the 10 hottest years in Boston have been since 2010,” said Stephen Young, a professor of environmental sustainability at Salem State University, citing federal data.

The 2021 climate stats are in! Boston & Providence set a new record for the warmest year in their respective station history. Worcester & Hartford came in at the 5th warmest. #mawx #ctwx #riwx pic.twitter.com/pMRDjIlx44

— NWS Boston (@NWSBoston) January 1, 2022

Nearby areas were abnormally warm in 2021, too. Providence saw its warmest year on record, beating out its previous temperature record set in 2020 by just .1 degree. It was also the fifth warmest year in Worcester and Hartford. An analysis led by Young, released just last week, found that New England is warming faster than the rest of the planet.

Young said that as the world warms up due to greenhouse gas emissions, the world’s oceans are absorbing excess heat. Coastal waters are heating up especially quickly, and the Gulf of Maine, just off the coast of Boston, is among the fastest-warming bodies of water on Earth.

“Given this understanding, are you surprised that Boston is warming so quickly?” he asked.

The occasional unseasonably balmy day may be nice, but all this warm weather is taking a massive toll on the region. Heat is particularly dangerous for low-income neighborhoods, which tend to absorb more heat due to abundant concrete and asphalt. High temperatures are also threatening local biodiversity, allowing more invasive species to thrive, and putting local industries — like agriculture, lobstering, and tourism — at risk.

Without urgent action to curb planet-warming pollution, Boston will warm even more quickly in the coming years. By 2035, studies show that the Northeast could be more than 3.6 degrees Fahrenheit hotter on average than it was before the Industrial Revolution.

“With the continued massive burning of fossil fuels, we can expect the oceans to continue their warming and the coastal area to continue to heat up ... and we will continually report on our region breaking more and more “hottest” records,” Young said.