Maryland Climate Bulletin (December)

[dallen7908]

 

 

Posting for State Climatologist:

 

"Maryland Climate Bulletin for December 2025, which includes sea surface temperatures for the Chesapeake Bay and the state's coastal waters, along with all its regular sections. 

You can access the Bulletin from the following link:

https://mdsco.umd.edu/Bulletin/bulletin_mdsco_current.pdf

Points to highlight are:

 

1) Statewide averages indicate that December 2025 was colder and drier than normal (i.e., 1991-2020 averages). The statewide mean temperature was much colder than normal (3.7°F below) in December, after a slightly colder-than-normal November (0.1°F below) and October (0.2°F below). Statewide precipitation was drier than normal (1.85 inches deficit) in December, following drier-than-normal November (1.73 inches deficit) and October (1.54 inches deficit).

 

2) The mean temperature was colder than normal throughout the state, particularly over Harford and Cecil counties (4.5‒4.8°F below), the counties of the Eastern Shore (3.9−4.5°F below), and the central Piedmont (3.6−4.2°F below). Precipitation was below normal in the entire state, particularly over the southern and western perimeters of the Piedmont (2.1‒2.2 inches deficit), the northern Piedmont (1.9‒2.0 inches deficit), and western Maryland and northern Eastern Shore (1.7‒1.9 inches deficit). In general, these regions received 50‒59% less precipitation than normal for the month, with western Montgomery and Frederick counties receiving the least (59‒62%).

 

3) Drought conditions worsened by the end of December. While the extent of the state affected by drought conditions remains the same as at the start of the month (~100%), the extent of Moderate and Severe drought conditions increased by approximately 10 and 20%, respectively. Moderate conditions covered the state westward of the Bay, with Severe conditions over Montgomery, Frederick, Washington, and Allegany counties, as well as portions of Garrett and Charles counties. Throughout the state, streams and rivers experienced Below-normal to Much-Below-normal streamflow, with more streams and rivers in the Much-Below-normal category than in November.

 

4) Statewide minimum daily temperatures from January 1 to December 31 indicated the number of freezing days with minimum temperatures equal to or colder than 32°F has been three days more than normal (93 vs. 90) with two freezing spells below normal (i.e., two or more consecutive freezing days; 12 vs. 14); twenty seven of these days, and two of the spells occurred in December.

 

5) Statewide daily total precipitation from January 1 to December 31 showed that the number of days with extreme precipitation (at least 0.64 inches ‒the 95th percentile in 1951−2000) has been five days below normal (14 vs. 19), with none in December. The number of dry spells (two or more consecutive days with daily precipitation of no more than 0.04 inches) for the calendar year has been also fewer than normal by two spells (46 vs. 48), with five of them occurring in December and the longest lasting seven days; the mean duration to date of the dry spells has been normal (5 days).

 

6) Statewide mean, maximum, and minimum temperatures in December 2025 (34.4, 43.4, 25.5°F) were below their (1895-2024) long-term means, but far from their coldest records (of 24.6, 33.2, and 16.0°F set in 1989). This month's mean, maximum, and minimum temperatures made this the forty-fourth, forty-seventh, and forty-second coldest December, respectively, since 1895.

 

7) Statewide precipitation in December 2025 (1.83 inches) was below its (1895-2024) long-term mean and within the 25% of its lowest values on record. Still, it was far from its record of 0.50 inches set in 1955. Statewide, this was the eighteenth-driest December since 1895, the sixteenth driest in Allegany and Garrett counties, the seventeenth in Montgomery County, and the nineteenth in Anne Arundel, Howard, and Washington counties.

 

8) Sea surface temperatures in the Chesapeake Bay in December 2025 were colder than their 2007-2020 mean everywhere, notably in the western coastal waters of the Middle Basin and southwestern Upper Basin, the Potomac River, the Chincoteague Bay, and the mouth of rivers in the Eastern Shore (5°F below). The all-basin mean temperature of 41.8°F was below the mean of the 2007-2020 base period (44.6°F) and far from the coldest December temperature in the 19-year data set (2007-2025), which was 38.7°F set in 2010.

 

Please see the Bulletin for more details, including information on century-long trends, climatology, standard deviation maps, and links of interest. 

 

The regular production of the Bulletin is only possible thanks to the hard work and data provided by our friends at NOAA National Centers for Environmental Information, the CoastWatch East Coast Node, the Institutions involved in the U.S. Drought Monitor, and the U.S. Geological Survey's Water Watch.

 

The Maryland Climate Bulletin is issued monthly and presents the state's recent air and sea surface temperatures and precipitation conditions in a clear, concise format, helping Marylanders better understand regional climate variations. Please help disseminate the Bulletin.

 

Thanks,

 

Alfredo

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............................................. 
Alfredo Ruiz-Barradas, PhD 

Associate Research Professor

Maryland State Climatologist"