Data Date: December

Raindrops on glass

Very Warm and Moist Conditions Characterize the 2015-2016 Winter Season Across Delaware

Posted on | by Dan Leathers
 
 

 

Winter Temperatures

Preliminary data indicates that winter temperatures were far above the 30-year “normal” during the winter season. The statewide mean winter temperature of 41.1°F was 4.8°F above the 1981-2010 mean value of 36.3°F (Figure 1). This made winter 2015-2016 the 4th warmest since records began in 1895.

Witer Precipitation

The statewide mean precipitation of 11.47 inches was 1.71 inches above the 1981-2010 normal of 9.76 inches, and was the 3rd year in a row with above normal winter precipitation (Figure 2).

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) show that winter temperatures across the entire State were above normal, with the largest anomalies found in northern Sussex and northern New Castle counties in Delaware and in Chester County, PA (Figure 3).

Winter precipitation varied significantly across the State depending upon location. In general, the heaviest precipitation fell across interior Sussex County, DE (Figure 4). At the New Castle County Airport, 22.7 inches of snow fell during the December through February winter season, a value slightly above the 1981-2010 mean.

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Drops of water on bright green grass

Temperature and Precipitation Both Above Normal Across Delaware During 2015

Posted on | by Dan Leathers
 
 
 

Annual Temperatures

Statewide mean annual temperature in 2015 was 56.4°F according to preliminary data from the National Climatic Data Center (NCDC). This was 1.0°F above the 1981-2010 normal of 55.4°F (Figure 1) and was the 11th warmest year in Delaware since 1895.

Monthly temperatures varied greatly throughout the year (Figure 2). The first three months of 2015 saw much below normal temperatures, including the 6th coldest February since 1895. The last nine months of the year saw above normal temperatures, except for October, which was slightly below normal. Tremendous warmth ended the year with December temperatures averaging 12.4°F above the 1981-2010 mean. December 2015 was the warmest December on record, smashing the old record by 6.1°F.

Annual Precipitation

Statewide precipitation in 2015 averaged 46.37 inches, 2.04 inches above the 1981-2010 mean of 44.33 inches (Figure 3).

Monthly precipitation anomalies varied between positive and negative throughout the year, with seven months of below normal and five months of above normal precipitation (Figure 4). June saw the largest precipitation anomaly of 5.30 inches above the 30-year normal, helping to push the annual value above the long-term mean.

Statewide Spatial Averages

According to data from the Delaware Environmental Observing System (DEOS; deos.udel.edu), mean annual temperature anomalies varied across Delaware (Figure 5). Northern New Castle County, much of Sussex County, southern Kent County and Chester County, PA all experienced above normal temperatures for the year. Coastal Sussex County and western portions of News Castle and Kent counties saw below normal mean annual temperatures.

Precipitation across the region varied substantially in 2015, ranging from just under 40 inches to greater than 50 inches at several locations across the State (Figure 6).

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A very bright Sun shines on an autumn leaf

December 2015: Extraordinary Warmth and Above Normal Precipitation Across Delaware

Posted on | by Dan Leathers

 

December Temperatures

Preliminary data indicates that the statewide average temperature in December was 50.5°F; this was 12.4°F above the 1981-2010 normal of 38.1°F (Figure 1), making December 2015 the warmest on record since 1895. This December was 6.1°F above the second warmest December on record that occurred in 2001. To put this in perspective, December 2015 was nearly 3.0°F above the November long-term average temperature and 6.0°F above the long-term average March temperature for the First State.

December Precipitation

Delaware’s statewide precipitation for December 2015 averaged 4.68 inches, 1.11 inches above the 1981-2010 mean (Figure 2). December 2015 saw no snowfall accumulations anywhere in the State.

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) shows the unprecedented warmth across all of Delaware and Chester County, PA (Figure 3). Several stations in northern New Castle County, DE and Chester County, PA saw anomalies between 13°F and 14°F above the 30-year normal for December.

Precipitation was above normal across the entire State, with the largest positive departures found across southern New Castle County (Figure 4).

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Barn in Snow

Cold and Snowy Conditions Dominate Delaware’s 2014-15 Winter Season

Posted on | by Dan Leathers
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Figure 1. Delaware statewide mean winter temperature (°F) 1895-1896 through 2014-15.

 
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Figure 2. Delaware statewide winter precipitation (inches) 1895-1896 through 2014-15.

 

Winter Temperatures

Preliminary data indicates that Delaware’s winter (December, January and February) temperature was below the 1981-2010 normal for the second year in a row. The Statewide mean winter temperature of 33.1°F was 3.2°F below the 30-year normal of 36.3°F. The 2014-15 winter season was the 30th coolest since records began in 1895 (Figure 1).

Winter Precipitation

Cold temperatures were accompanied by above normal precipitation across the state during the winter season. The statewide mean precipitation of 11.05” was 1.29” above the 1981-2010 normal of 9.76”, and was the second winter in a row with above normal values, and the 34th wettest winter since records began in 1895 (Figure 2).

Statewide Spatial Averages

Mean winter temperatures across the state were cold throughout, with temperatures ranging from 2.5°F to as much as 6.5°F below the 30-year mean (Figure 3). Precipitation across the State was highest across Sussex County, with values of over 12 inches in several locations (Figure 4). Winter precipitation values were lower over New Castle County, DE and Chester County, PA, with values generally less than 10 inches.

The colder than normal temperatures, combined with ample precipitation resulted in snowfall totals that were generally above normal across most of the State. Fifteen snowfall events dropped measurable snow on the First State during the winter season. Snowfall during the months of November through March (Delaware’s typical snowfall season) was greater than 20 inches across most of northern New Castle County, DE and Chester County, PA (Figure 5). Snowfall across Kent and Sussex Counties generally ranged from 13 to nearly 20 inches.

Winter 2014-15 average temperature departures from the 1981-2010 mean based upon DEOS station data.
Figure 3. Winter 2014-15 average temperature departures from the 1981-2010 mean based upon DEOS station data.

 
Winter 2014-15 precipitation based upon DEOS station data.
Figure 4. Winter 2014-15 total precipitation based upon DEOS station data.

 
Winter 2014-15 snowfall totals based upon DEOS station data.
Figure 5. Winter (November through March) 2014-15 snowfall totals based upon DEOS station data.
Rocks and Ice

Warm Temperatures and Near Normal Precipitation Characterize Delaware’s Climate during December 2014

Posted on | by Dan Leathers
Posted on Tue 01/20/15 , Updated 02/03/15

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Figure 1. Delaware statewide mean December temperature (°F) 1895-2014.
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Figure 2. Delaware statewide mean December precipitation (inches) 1895-2014.

December Temperatures

Preliminary data indicates that the statewide average temperature in December was 41.7°F, which is 3.6°F above the 1981-2010 normal of 38.1°F (Figure 1). In addition, December 2014 is the fourth December in a row with above normal temperatures. December 2014 is tied with December 1972 as the 14th warmest since records began in 1895, and falls 107th on NCDC’s 120 year ranking from coldest to hottest Decembers. [More information on NCDC’s Climatological Ranking can be found here.]

December Precipitation

Delaware’s preliminary statewide precipitation total for December 2014 averaged 3.66 inches, which is 0.09 inches above the 1981-2010 mean (Figure 2). Thus, precipitation during the month of December was very close to normal.

Statewide Spatial Averages

All stations across the Delaware Environmental Observing System (DEOS) network experienced higher than normal temperatures during December (Figure 3). Temperature anomalies were greatest in northern Delaware and in Chester County, PA, where some stations had positive anomalies greater than 4.0°F.

Precipitation generally increased from south to north across the region ranging from 5 inches in coastal Sussex County to less than three inches in portions of northern Delaware and Chester County, PA (Figure 4).

December 2014 average temperature departures from the 1981-2010 mean based upon DEOS station data.

Figure 3. Dec 2014 average temperature departures from the 1981-2010 mean based upon DEOS station data.
Dec 2014 total precipitation based upon DEOS station data.

Figure 4. December 2014 total precipitation based upon DEOS station data.
 
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Cars in Wilmington

Cool Temperatures and Near Normal Precipitation Characterize Delaware’s Climate During 2014

Posted on | by Dan Leathers
Posted on Mon 01/26/15 , Updated 02/01/16

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Figure 1. Delaware statewide annual mean temperature (°F) 1895-2014.
December monthly temperature anomalies.

Figure 2. Delaware monthly temperature anomalies.

Annual Temperatures

Statewide mean annual temperature in 2014 was 54.8°F according to preliminary data from the National Climatic Data Center (NCDC). This was 0.6°F below the 1981-2010 normal of 55.4°F (Figure 1) and was the coolest year in Delaware since 2003.

Monthly temperatures varied greatly throughout the year (Figure 2). The first four months of 2014 saw much below normal temperatures accompanied by heavy snowfall across the State. Although late spring and early summer saw a return to above normal temperatures, the late summer climate was cooler than normal, a welcome respite from the summer heat for many residents. The year ended with a return to warmth in three of the last four months.

Annual Precipitation

Statewide precipitation in 2014 averaged 43.49 inches, 0.84 inches below the 1981-2010 mean of 44.33 inches (Figure 3).

Monthly precipitation anomalies varied between positive and negative throughout the year, with six months of above normal and six months of below normal precipitation (Figure 4). None of the monthly precipitation anomalies were large, leading to the near normal annual total.

Statewide Spatial Averages

According to data from the Delaware Environmental Observing System (DEOS; deos.udel.edu), mean annual temperatures were below normal across the entire State with the largest negative anomalies found in coastal Sussex County (Figure 5).

Precipitation across the region varied substantially in 2014, ranging from just under 39 inches to greater than 50 inches across the region (Figure 6).

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Figure 3. Delaware statewide annual precipitation (inches) 1895-2014.
Delaware monthly precipitation anomalies.

Figure 4. Delaware monthly precipitation anomalies.
2014 mean annual temperature departures from the 1981-2010 mean based upon DEOS station data.

Figure 5. 2014 mean annual temperature departures from the 1981-2010 mean based upon DEOS station data.
2014 annual precipitation totals based upon DEOS station data.

Figure 6. 2014 annual precipitation totals based upon DEOS station data.
 
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Snow on Barn

Winter 2013-2014 Climate Update

Posted on | by Dan Leathers

Below normal temperatures and heavy snowfall characterized Delaware’s Climate during the 2013-2014 winter season.

 

Winter Temperatures

Preliminary data indicates that Delaware’s winter temperature was below the 1981-2010 normal for the third time in the last five years. The Statewide mean winter temperature of 34.9°F was 1.4°F below the 30-year normal of 36.3°F. Although slightly cooler than normal, this winter’s temperature was actually near the middle of all winters since records began in 1895 (Figure 1).

Winter Precipitation

Cold temperatures were accompanied by above normal precipitation across the state during the winter season. The statewide mean precipitation of 12.35” was 2.59” above the 1981-2010 normal of 9.76”, and was the first winter since 2009-2010 with above normal values (Figure 2), and the 18th wettest winter since records began in 1895.

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) show that mean winter temperatures across the state were cold throughout, with the coldest conditions found along coastal Sussex County and in sections of northern Kent and southern New Castle Counties (Figure 3). The spatial patterns of average maximum (Figure 4) and minimum (Figure 5) temperatures were similar to that of the mean winter temperature across the First State.

The colder than normal temperatures, combined with above normal precipitation resulted in heavy snowfall totals across the entire State during the 2013-2014 snowfall season. More than twice the seasonal average fell across the entire state with some locations receiving nearly three times their average accumulations. Snowfall totals ranged from over 50 inches in northern New Castle County and Chester County, PA to greater than 25 inches across extreme southern portions of Delaware.

 
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Water in Winter

Warm and Wet Conditions Return to Delaware During December 2013

Posted on | by Dan Leathers

 

Delaware’s Climate during December 2013 was characterized by warmer than normal temperatures and above normal precipitation values. Although temperatures were above normal across the State, two significant snowfall events reminded residents that winter had arrived.

 

December Temperatures

Statewide average temperature in December was 41.8°F according to preliminary data from the National Climatic Data Center (NCDC). This was 3.4°F above the 1981-2010 normal of 38.4°F (Figure 1) and was the third December in a row with above normal temperatures.

December Precipitation

Statewide precipitation in December averaged 5.05 inches, 1.41 inches above the 1981-2010 mean of 3.64 inches (Figure 2). Many areas of the state saw substantial snowfall during the month with portions of northern Delaware receiving nearly 12 inches.

Statewide Spatial Averages

Mean monthly temperatures were above normal across the majority of the DEOS (deos.udel.edu) network in December, with the greatest warmth found in southern Kent and Sussex Counties (Figure 3). Maximum temperature anomalies across the State were similar to the pattern of mean monthly temperatures (Figure 4). Average minimum temperatures were above normal at all locations except coastal and southern Sussex County where they were near or just below normal (Figure 5).

Precipitation was above normal throughout Delaware, with higher than normal values generally increasing from north to south (Figure 6).

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Rainbow over Bridge

2013 Warm and Wet Across Delaware

Posted on | by Dan Leathers

Delaware’s 2013 climate was characterized by slightly warmer than normal temperatures and above normal precipitation values.

 

Annual Temperature

Statewide mean annual temperature in 2013 was 56.5°F according to preliminary data from the National Climatic Data Center (NCDC). This was 0.7°F above the 1981-2010 normal of 55.8°F (Figure 1) and was the fourth year in a row with above normal temperatures. However, this year was nearly 2.0°F cooler than 2012’s all time high value of 58.4°F.

Annual Precipitation

Statewide precipitation in 2013 averaged 49.93 inches, 4.07 inches above the 1981-2010 mean of 45.86 inches (Figure 2). Most areas of the state saw substantially above normal precipitation during the summer months, making the summer of 2013 the 5th wettest on record since 1895.

Statewide Spatial Averages

According to data from the Delaware Environmental Observing System (DEOS; deos.udel.edu), mean annual temperatures were above normal across portions of New Castle, western Kent and Sussex counties, and across Chester County, PA (Figure 3). Mean annual temperatures were below normal across the remainder of the State.

Precipitation was much above normal in all locations except southwestern Kent County and portions of Chester County, PA (Figure 4). The largest positive precipitation departures were found along the eastern portions of Sussex County where some locations received 10 inches more precipitation than normal.

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Snow in Park

December 2013: 4th snowiest in Wilmington since 1948!

Posted on | by Dan Leathers

Three early season snowfall events propelled December 2013 into 4th place on the list of all-time snowiest Decembers for the Wilmington area with 11.9” of snow. This was more than 8.0” above the December normal of 3.5”.

 

A surprise snowfall associated with heavy bands of precipitation moved through the region on Sunday, December 8th, dropping 8.5” of snow at the Wilmington/New Castle County Airport. This was followed by another fast moving system on Tuesday the 10th that dropped another 2.9” of snow in the Wilmington area. Another 0.5” of snow fell on Saturday the 14th before precipitation changed to freezing rain and rain. The second half of the month was snow free except for some trace amounts.

Wilmington’s snowiest December on record occurred in 1966 when 21.5” of snow fell at the Wilmington Airport during the month. 2009 was also a “December to remember” when 19.7” of snow fell in the Wilmington area. The graph of December monthly snowfall totals (Figure 1) shows the variability in early season snowfall since 1948 for the Wilmington/New Castle County Airport.

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