October 2021 – Very Warm with Near Normal Precipitation Across Delaware

October Temperatures

Preliminary data indicates that the statewide average temperature in October was 63.9o F, which is 6.8o F above the 1981-2010 mean value of 57.1o F (Figure 1).  October’s average temperature was the second highest recorded since observations began in 1895.  Only October 2007 has seen a higher mean temperature.

October Precipitation

Delaware’s statewide precipitation for October 2021 averaged 3.65 inches, 0.19 inches above the 1981-2010 mean (Figure 2).  This placed this month’s precipitation total in the normal range of all years since 1895.

Statewide Spatial Anomalies

Data from the Delaware Environmental Observing System (DEOS) show that temperature departures were far above normal across the entire State, with many stations seeing positive temperature anomalies of greater than 6o F (Figure 3).  Precipitation anomalies varied across the State with mostly positive precipitation anomalies found across Kent and New Castle Counties, and mixed anomalies across Sussex County (Figure 4).

National Anomalies

Temperatures were much above normal across the eastern two-thirds of the United States, with the largest positive temperature anomalies found across the Great Lakes and Northeast regions.  Much of the Pacific Coast and the Southwest experienced below normal temperatures during the month (Figure 5).  Precipitation anomalies varied greatly across the country (Figure 6), with excessively heavy precipitation falling in northern California.  The 500 hPa height pattern for October shows a very strong jet stream ridge located over eastern North America contributing to the extreme warmth across that region (Figure 7).

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Wet rain on fresh grass

October 2020 – Warm and Wet Across Delaware

October Temperatures

Preliminary data indicates that the statewide average temperature in October was 60.8o F, which is 3.7o F above the 1981-2010 mean value of 57.1o F (Figure 1).  October 2020 was tied with 1990 as the 9th warmest October since observations began in 1895.

October Precipitation

Delaware’s statewide precipitation for October 2020 averaged 5.16 inches, 1.70 inches above the 1981-2010 mean (Figure 2), placing this month’s precipitation total in the top one-third of all months since 1895

Statewide Spatial Anomalies

Data from the Delaware Environmental Observing System (DEOS) show that temperature departures were positive at all stations, with the largest anomalies found across Sussex County (Figure 3).  Precipitation was above normal throughout the State, with departures of greater than four inches across much of southern Delaware (Figure 4). 

National Anomalies

Temperatures were above normal across the western and eastern portions of the United States (3 – 7o F), while below normal temperatures were found across the Great Plains, especially from Montana east through Minnesota (Figure 5).  Precipitation was far below normal across the southwestern portions of the country, with above normal precipitation covering much of the eastern one-third of the United States (Figure 6).  The 500 hPa height pattern for October exhibits a strong trough across the north-central portions of the country and ridging along both the Atlantic and Pacific coasts (Figure 7).

 

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October 2019 – Warm and Moist Across Delaware

October Temperatures

Preliminary data indicates that the statewide average temperature in October was 61.3°F, which is 4.2°F above the 1981-2010 mean value of 57.1°F (Figure 1). This places October 2019 as the 8th warmest since records began in 1895.

October Precipitation

Delaware’s statewide precipitation for October 2019 averaged 4.38 inches, 0.92 inches above the 1981-2010 mean (Figure 2). This placed the October 2019 precipitation amount in the top one-third of months since 1895.

Statewide Spatial Anomalies

Data from the Delaware Environmental Observing System (DEOS) show that temperature departures were uniformly above normal throughout the State (Figure 3), with the largest positive anomalies found across northern New Castle County. Precipitation was above normal at all stations across New Castle and Kent Counties (Figure 4), with several stations in Sussex County recording near or just below normal precipitation for the month.

National Anomalies

Temperatures were above normal throughout the eastern portion of the U.S, where some positive anomalies reached greater than 5°F (Figure 5). The western two-thirds of the U.S. saw below normal temperatures for the month, with some parts of the Rocky Mountains recording temperatures more than 10°F below normal. In general, precipitation was below normal across the western U.S. and above normal across the east (Figure 6). The 500 hPa height pattern for October showed a strong trough dominating the western U.S. (Figure 7), bringing the cold temperatures to that region.

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Rain drops on an autumn leaf

October 2018: Warm and Wet Conditions Persist Across Delaware

 

 

 

October Temperatures

Preliminary data indicates that the statewide average temperature in October was 60.3°F, which is 3.2°F above the 1981-2010 mean value of 57.1°F (Figure 1). October 2018 tied October of 2016 as the 11th warmest on record since 1895. Our warm October followed record setting warmth during September. The mid-Atlantic and Southeastern United States shared in this warmth with many areas seeing temperatures 3° – 5°F above normal (Figure 2).

October Precipitation

Delaware’s statewide precipitation for October 2018 averaged 4.95 inches, 1.49 inches above the 1981-2010 mean (Figure 3). This continued a string of four months with above normal precipitation across the First State.

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) show that temperature (Figure 4) departures were positive throughout the State, with the largest departures across Sussex County. Precipitation departures were positive across the southern two-thirds of the State, while many locations in New Castle County actually saw below normal precipitation (Figure 5).

 
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Autumn leaves shine in the bright Sun

Warm and Dry Conditions Characterize the 2017 Autumn Season Across Delaware

 

Autumn Temperatures

Preliminary data indicates that autumn 2017 ranked as the 3rd warmest autumn season since records began in 1895 (tied with three other autumn seasons). The statewide mean autumn temperature of 60.2°F was 2.6°F above the 1981-2010 mean value of 57.6°F (Figure 1).

Autumn Precipitation

The statewide mean precipitation of 8.23 inches was 2.60 inches below the 1981-2010 normal of 10.83 inches, and was in the driest one-third of autumns since 1895 (Figure 2). Precipitation during the autumn of 2017 was the lowest since the 2013 season.

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) show that autumn temperature anomalies were generally positive across the State, with a few locations experiencing near normal temperatures for the season (Figure 3).

Autumn precipitation was much below normal across the entire State, with the exception of extreme southeastern Sussex County (Figure 4). However, the size of the negative anomalies varied greatly from one location to another. Several stations in northern New Castle County and Chester County, PA saw negative anomalies of between four and six inches during the autumn months.

 

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Autumn leaves illuminated by the Sun

October Climate Conditions – Very Warm with Near Normal Precipitation Across Delaware

 

 

October Temperatures

Preliminary data indicates that the statewide average temperature in October was 62.6°F, which was 5.5°F above the 1981-2010 normal of 57.1°F (Figure 1). October 2017 was the 2nd warmest October since 1895. Only October 2007 has been warmer.

October Precipitation

Delaware’s statewide precipitation for October 2017 averaged 3.69 inches, 0.23 inches above the 1981-2010 mean (Figure 2), placing it just above normal for the month.

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) show that temperatures were above normal across the entire State with the largest positive temperature departures found across Chester County, PA and northern New Castle County, DE. (Figure 3). Precipitation departures varied according to location across the region (Figure 4), with no departures greater than two inches.

 

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Golden sky, dark clouds, and rain

Very Warm, and Moist Conditions Characterize the 2016 Autumn Season Across Delaware

 

 

Autumn Temperatures

Preliminary data indicates that temperatures were significantly above the 30-year normal during the autumn season. The statewide mean autumn temperature of 60.3°F was 2.7°F above the 1981-2010 mean value of 57.6°F (Figure 1). Autumn 2016 was tied with the 2005 season as the 2nd warmest autumn since records began in 1895.

Autumn Precipitation

The statewide mean precipitation of 13.23 inches was 2.40 inches above the 1981-2010 normal of 10.83 inches (Figure 2). However, much of the autumn total fell during September, when 9.43 inches of precipitation fell across the State, the 3rd wettest September total on record.

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) show that autumn temperatures were much above normal across northern New Castle County and Chester County, PA, along with southern portions of Kent and northern Sussex counties (Figure 3).

Autumn precipitation varied appreciably across the State depending upon location. Very dry conditions were especially apparent across extreme northern Delaware and Chester County, PA (Figure 4), while southern Delaware saw much above normal precipitation during the autumn Season.

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Fall leaves

October 2016 Brings Warm and Dry Conditions Across the First State

 

October Temperatures

Preliminary data indicates that the statewide average temperature in October was 60.0°F, 2.9°F above the 1981-2010 normal of 57.1°F (Figure 1). October 2016 ranks as the 12th warmest October since records began in 1895. October was the fourth month in a row with temperatures appreciably above normal.

October Precipitation

Delaware’s statewide precipitation for October 2016 averaged 3.02 inches, 0.44 inches below the 1981-2010 mean of 3.46 inches (Figure 2). Precipitation amounts varied greatly, with dry conditions across northern Delaware and wetter conditions in the southern portion of the State.

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) shows that temperatures were above normal across the entire State, with the largest temperature anomalies found across Chester County, PA and inland Sussex County (Figure 3). Much below normal rainfall was the rule across northern New Castle County, and Chester County, PA, while precipitation was generally above normal across Sussex County (Figure 4).

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Drops of water on bright green grass

Temperature and Precipitation Both Above Normal Across Delaware During 2015

 
 
 

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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Trees in Autumn

Autumn 2014 Slightly Dry with Near Normal Temperatures Across Delaware

Autumn Temperatures

de_statewideAutumnTemp-1895-2014_0.png
Figure 1. Delaware Statewide mean Autumn Temperature (°F) 1895-2014.

Preliminary data indicates that the statewide mean autumn temperature of 57.8°F was 0.2°F above the

1981-2010 normal of 57.6°F (Figure 1). The near normal autumn temperatures followed four consecutive seasons with below normal temperatures across Delaware. Temperatures

de_monthlyTempAnom_2014.png
Figure 2. Delaware statewide temperature anomalies for January 2014 through November 2014.

have been quite variable across the State during the year (Figure 2), with seven of the first eleven months being below normal.

Autumn Precipitation

Near normal autumn temperatures were accompanied by slightly dry conditions across the state during the autumn season. The statewide

de_statewideAutumnPrecip-1895-2014_0.png
Figure 3. Delaware Statewide mean Autumn Precipitation (°F) 1895-2014.

mean precipitation of 9.52 inches was 1.31 inches below the 1981-2010 normal of 10.83 inches (Figure 3). Monthly precipitation anomalies have varied between positive and negative during the year, but

no month has seen large departures from normal (Figure 4).

de_monthlyPrecipAnom_2014_0.png
Figure 4. Delaware statewide precipitation anomalies for January 2014 through November 2014.

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) show that temperatures varied considerably across the State during the autumn season (Figure 5), with generally small positive or negative departures at most stations. The largest departures were found along the coastal areas of Sussex County where cool conditions were dominant.

Precipitation varied from as low as 7.51 inches along the Atlantic Coast to a high of 14.52 inches in western Chester County, PA. Even with this large variation, most stations in the region experienced slightly dry conditions during the season, with the greatest negative anomalies found along the Atlantic Coast and in northern Chester County, PA (Figure 6).

Autumn 2014 average temperature departures
Figure 5. Autumn 2014 average temperature departures from the 1981-2010 mean based upon DEOS station data.
Autumn 2014 precipitation departures
Figure 6. Autumn 2014 precipitation departures from the 1981-2010 mean based upon DEOS station data.