The New York Times kindly publishes a year-end summary of Boston’s weather for 2021. Most of that information probably applies to Maynard, perhaps with the exception that winter storms bringing only rain to Boston deposit some of that precipitation as snow in Maynard and points west.
Boston’s average temperature for the year was 54.6 degrees, 2.5 degrees above the long-term normal, making 2021 the second-warmest year since record taking began in 1872. This was on top of a long-term warming trend that has seen the Massachusetts state average annual temperature go from 47.3 to 48.3 degrees. The Boston average for June was the highest ever for that month; August and September the second highest for those months. Even modest increases in temperature have consequences. Winter has become shorter.
At Boston’s Arnold Arboretum, peak lilac blooming time has shifted from late to early May. The Arboretum contains 408 lilac plants representing 179 kinds, making it one of the premier lilac collections in North America. Lilac Sunday 2022 is planned for May 8th. Back at the beginnings, more than 110 years ago, Lilac Sunday was the last Sunday in the month.
Precipitation for 2021 was 52.33 inches; 8.74 inches above normal. And precipitation was not normally distributed. Long-term averages show precipitation as rain and melted snow in range of 3.5 to 5.0 inches depending on month. The pattern for 2021 was below average for January though March and again for November and December, but above average for April through October. July was exceptionally wet, recording 10 inches of rain for the second wettest July ever, followed by 7 inches in August and 7.5 inches in September. Homeowners did not have to water lawns, but it was a tough year for house painters and roofers.
Massachusetts records dating to before 1900 show that average annual precipitation was in range of 35 to 40 inches per year, gradually but consistently increasing to more recent averages of 45 to 50 inches. This is not just a local phenomenon. Nationally, east of the Mississippi River has become wetter while west has become drier. One not-surprising consequence of the trend for wetter years is more water in the Assabet River. Record keeping by the U.S. Geological Survey dates back to 1942, and shows that average river water volume has increased by 40 percent over that time span. Every year, rain and snowmelt far exceed Maynard's water needs, but the town has no active reservoir to retain surface water, and so is dependent on what seeps down to the aquifer to supply our town wells. Perennially, Maynard considers reviving White Pond, south of Lake Boon as a water supply. The pond had served Maynard, 1888-1999. A 2019 report estimated the cost of building a water treatment plant and installing miles of new pipe at about $30 million dollars.
This winter is off to a slow snow start. Long-term Boston average is 42 inches. Starting October 1, 2021, Boston has had only 12.2 inches of snow. Unless the last days of January and all of February and March bring unexpectedly large amounts, this will have been a poor year for sledding, skiing, snowplowing, snowmobiles, snowmen and snowball fights.
We may be on the verge of a tipping point. Until recently, one surprising consequence of warmer and wetter was that while winter was becoming shorter, it was also wetter, thus packing more snow into a shorter season. The winter of 2014-15 set an all-time Boston record at 108.6 inches. Of the ten snowiest winters dating back to 1890, seven has been in the last 30 years. However, there may come a time when are temperatures are warm enough that winter precipitation will be less snow and more ice, sleet and rain. When it comes, the crossover will affect Boston before it impacts the inland cities and towns.