Martin said there's been a strong ridge of high pressure that's been "more or less stationary" off of the East Coast pumping in warm air, plus another low pressure system located over Lake Superior — and combined, they're bringing tropical moisture northward.
"It's a pattern that has been common this month, and right now it is passing an extreme," Martin said.
Clouds overhead kept Thursday's temperature from setting a new monthly record, though. The all-time record for December in Baltimore is 77 degrees, set on Dec. 29, 1984 and again on Dec. 6 and Dec. 7 in 1998.
Christmas Day will see warm weather again with a high of 68 degrees and a 70 percent chance of rain during the day.
Saturday will have a high of 60 and a chance of rain again, at 60 percent.
Sunday will have a high near 70 and a 30 percent chance of rain.
By Monday, the weather will turn more seasonable, with a high temperature of 46 degrees, but expect a warm-up into the 50s for Tuesday and Wednesday.
All is not lost for winter weather lovers, Martin said. Those who've lived in Maryland long enough know that winter weather can be highly variable and the El Nino pattern could fuel strong storms -- and those could be snowstorms if the weather cools off.
"It's not atypical to see large fluctuations in temperature in the winter," Martin said. "Of course, this is a bit on the extreme side."
Baltimore Sun reporter Colin Campbell contributed to this article.