A mild December helped put 1990 into the record books as the warmest year in 120 years of official recordkeeping in both Baltimore and Washington and the second-warmest year in Virginia.
And the region wasn't alone in its historic warmth: 1990 was the third-hottest year on record in the lower 48 states and may have been the hottest globally, meaning seven of the warmest years on record worldwide have occurred since the beginning of the 1980s.
"It was a mild year," said Ken Shaver, a National Weather Service forecaster at Baltimore-Washington International Airport. "But is there a trend here? Just remember what it was like December a year ago."
December 1989 was the coldest December recorded in Baltimore, with an average temperature of 25.4 degrees, more than 11 degrees below normal. For 14 days, the temperature never climbed above freezing.
By contrast, 1990's final month bowed out as the fourth-warmest on record, averaging 42.2 degrees at BWI and at the Custom House in Baltimore, where the weather service began keeping track in 1871.
Two high-temperature records were broken at the airport last month, two were tied, and Dec. 23 featured the warmest minimum temperature, 59 degrees, recorded for the month.
And such balmy, unseasonable weather was enough to boost the annual average temperature to 61.1 degrees at the Custom House. That was 3.2 degrees above normal, topping the record of 59.2 degrees set in 1931 and tied in 1949.
The 57.9 degree annual temperature average at BWI was 2.8 degrees above normal, the warmest measured since recordkeeping began when the airport opened in 1951. The previous warmest year was 1953, with an average temperature of 57 degrees.
In nearby Washington, the 1990 average temperature recorded at National Airport soared to 60.2 degrees, breaking the record of 59.5 degrees set in 1980. Virginia recorded its second-warmest year, at 58 degrees.
"Most of this record was put in place last winter, when the normally cold months turned out to be mild," said Mr. Shaver. "The summer months were fairly average as far as temperatures go."
Average temperature for January was 9.3 degrees above normal, February was 7.6 degrees above normal, and March was 4.3 degrees above normal, including four straight days of record-setting temperatures in the 80s at the airport. Only May, August and September had temperatures that were slightly below normal.
Precipitation for 1990 measured 41.9 inches at BWI, just a shade above the normal. But snowfall alone totaled just 8.1 inches, with more than half, 4.8 inches, accumulated during the Dec. 27 storm. Average annual snowfall in Baltimore is 21.6 inches.
Has the "greenhouse effect" -- the global warming predicted by climatologists as carbon dioxide and other heat-trapping gases are pumped into the atmosphere by industrialized society -- arrived?
"One year, or even one decade, doesn't prove a pattern. Try convincing the citrus growers out in California right now we've got global warming," said Mr. Shaver, referring to the recent Arctic deep freeze that severely damaged crops in the West.
He cheerfully pointed out the shortcomings of understanding climate and predicting weather, including the 90-day long-range forecast released last week. It calls for a 57 percent chance of above-normal temperatures during January, February and March in Maryland.
The problem? The previous three-month winter forecast, issued in late November, predicted a 60 percent to 65 percent chance of colder-than-normal temperatures.