July 2021 – Warm and Wet Across Delaware

July Temperatures

Preliminary data indicates that the statewide average temperature in July was 78.4o F, which is 1.8o F above the 1981-2010 mean value of 76.6o F (Figure 1).  The statewide temperature in July 2021 was tied as the 14th warmest since observations began in 1895.

July Precipitation

Delaware’s statewide precipitation for July 2021 averaged 5.75 inches, 1.61 inches above the 1981-2010 mean (Figure 2).  This placed this month’s precipitation total in the top one-third of all years since 1895.

Statewide Spatial Anomalies

Data from the Delaware Environmental Observing System (DEOS) show that temperature departures were above normal across the majority of the State (Figure 3).  Precipitation varied greatly across the State due to localized areas of convective (thunderstorm) activity during the month (Figure 4).

National Anomalies

Temperatures were generally below normal across much of the southeastern and southcentral United States, and New England.  Warmer than normal temperatures were found across the western one-third of the country, and across the mid-Atlantic region (Figure 5).  Some temperature anomalies were greater than 15o F for the month across the Pacific Northwest.  Precipitation anomalies varied greatly across the country with dry conditions in much of California and the Northwest United States.  Pockets of very wet conditions were found across portions of Texas and New England (Figure 6).  The 500 hPa height pattern for July shows a strong jet stream ridge located over the western United States and Canada (Figure 7), leading to the very warm and dry conditions across this region.

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Rain droplets on grass blade

July 2020 – Record Warmth and Very Wet Across Delaware

July Temperatures

Preliminary data indicates that the statewide average temperature in July was 81.0o F, which is 4.4o F above the 1981-2010 mean value of 76.6o F (Figure 1).  July 2020 was the warmest July since observations began in 1895, and it is the warmest of any month on record since 1895 for Delaware.

July Precipitation

Delaware’s statewide precipitation for July 2020 averaged 6.42 inches, 2.28 inches above the 1981-2010 mean (Figure 2).  The July 2020 precipitation amount was the 17th wettest since 1895, placing this month in the wettest one-third of all Julys since the start of observations.

Statewide Spatial Anomalies

Data from the Delaware Environmental Observing System (DEOS) show that temperature departures were above normal throughout the State (Figure 3).  Precipitation was likewise above normal at nearly all locations (Figure 4).

National Anomalies

Temperatures were above normal across most of the eastern one-third of the country, while below normal temperatures were found in both the northwest United States and along the Pacific coast (Figure 5).  Precipitation varied greatly across the country as is common when convective rainfall dominates during the summer months (Figure 6).  The 500 hPa height pattern for July showed a ridge dominating the eastern portion of North America leading to generally warm weather across that region (Figure 7).

 

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July 2019 – Very Warm with Near Normal Precipitation Across Delaware

July Temperatures

Preliminary data indicates that the statewide average temperature in July was 79.4°F, which is 2.8°F above the 1981-2010 mean value of 76.6°F (Figure 1). This places July 2019 as the 6th warmest since records began in 1895.

July Precipitation

Delaware’s statewide precipitation for July 2019 averaged 3.79 inches, 0.35 inches below the 1981-2010 mean (Figure 2). Delaware’s July precipitation was in the middle 0ne-third of values for the last 125 years, putting it into the “normal” range for this month.

Statewide Spatial Anomalies

Data from the Delaware Environmental Observing System (DEOS) show that temperature departures were above normal throughout the State (Figure 3), with many stations seeing positive anomalies greater than 2.0°F. There was a mixture of positive and negative precipitation departures observed across the State (Figure 4). In general, northern New Castle County had greater than normal precipitation, while Kent and Sussex Counties saw below normal precipitation amounts during the month.

National Anomalies

The northeast quarter of the United States experienced above normal temperatures during July, with mixed temperature anomalies found throughout the rest of the country (Figure 5). Precipitation anomalies across the U.S. varied greatly, with above normal precipitation falling across the northern Great Plains, the southern Mississippi Valley and parts of the mid-Atlantic (Figure 6). In general, the southwest United States and California were dryer than normal. The 500 hPa height pattern for July showed weak anomalous ridging over the northeast portion of the Country (Figure 7), bringing the warm temperatures to that region.

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Foam from gentle waves glides over sand

2018 Summer Season Warm with Near Normal Precipitation Across Delaware

 

 

Summer Temperatures

Preliminary data indicates that summer temperatures averaged 76.2°F during the summer season, 1.7°F above the 30-year “normal” of 74.5°F (Figure 1). Summer 2018 is tied with the summer of 2005 as the 6th warmest since records began in 1895.

Summer Precipitation

The statewide mean precipitation of 13.73 inches was 1.73 inches above the 1981-2010 normal of 12.0 inches. (Figure 2). This value placed the summer of 2018 in the “normal” range for precipitation since 1895.

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) show that summer temperature anomalies across the State were generally above normal, except for extreme western portions of Kent County (Figure 3). Summer precipitation totals varied greatly with location across the State (Figure 4). In general, stations in New Castle and Kent counties saw above normal precipitation during the summer season, while coastal areas of Sussex County saw significant precipitation deficits.

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Voluminous clouds illuminated by sun

July 2018 was Warm and Wet Across Delaware

 

 

 

July Temperatures

Preliminary data indicates that the statewide average temperature in July was 77.3°F, which is 0.7°F above the 1981-2010 mean value of 76.6°F (Figure 1). July 2018 ranked in the top one-third for temperatures since 1895. During the month, 10 days at or above 90°F were recorded at the Wilmington/New Castle County Airport, approximately one more than average. Larger positive temperature anomalies were found across the rest of the northeast United States, and across most of the western and southwestern portions of the country (Figure 2).

July Precipitation

Delaware’s statewide precipitation for July 2018 averaged 5.68 inches, 1.54 inches above the 1981-2010 mean (Figure 3), placing this month in the wettest one-third of Julys since 1895. Although statewide totals for July were above normal, the month actually began very dry across most of the state, with approximately 80% of the month’s precipitation falling after July 20th.

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) show that temperature (Figure 4) departures were generally small and varied between positive and negative values across the State during July. Precipitation departures also varied greatly from one location to another (Figure 5), but were generally positive contributing to the wet conditions statewide. Some locations saw precipitation anomalies more than four inches above normal.

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Water drops collect on green plants

Warm and Wet Conditions Characterize the 2017 Summer Season Across Delaware

 
 

Summer Temperatures

Preliminary data indicates that summer 2017 ranked as the 15th warmest summer season since records began in 1895 (tied with the 1995 and 2008 summer seasons). The statewide mean summer temperature of 75.3°F was 0.8°F above the 1981-2010 mean value of 74.5°F (Figure 1).

Summer Precipitation

The statewide mean precipitation of 18.24 inches was 6.24 inches above the 1981-2010 normal of 12.0 inches, and was the 12th wettest summer season since 1895, and the 5th year in a row with above normal summer precipitation (Figure 2).

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) show that summer temperature anomalies varied between positive and negative, depending upon location within Delaware and Chester County, PA (Figure 3). The Wilmington/New Castle County Airport recorded 16 days of temperatures greater than or equal to 90°F, very near the 1948 – 2017 normal of 17 days.

Summer precipitation was above normal across the entire State (Figure 4). However, the size of the positive anomalies varied greatly from one location to another. The variable pattern of precipitation is due to the small-scale nature of convective storms; dropping heavy precipitation in some areas, while leaving others relatively dry.

 

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The Sun shining brightly upon grasses

July 2017: Warm and Very Wet Conditions Across the First State

 

 

 

July Temperatures

Preliminary data indicates that the statewide average temperature in July was 78.4°F; this was 1.8°F above the 1981-2010 normal of 76.6°F (Figure 1). July 2017 was the 12th warmest July since statewide records began in 1895.

July Precipitation

Delaware’s statewide precipitation for July 2017 averaged 8.47 inches, 4.33 inches above the 1981-2010 mean of 4.14 inches (Figure 2). This was the highest statewide precipitation total since September 2016, and the 6th wettest July since 1895.

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) shows that temperatures varied significantly across the state depending upon location (Figure 3). Precipitation was above the long-term mean at all sites statewide, with the largest positive anomalies found in northern New Castle and western Sussex counties (Figure 4).

 

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Pink flowers

Very Warm Temperatures and Near Normal Precipitation Characterize the 2016 Summer Season Across Delaware

 

Summer Temperatures

Preliminary data indicates that summer 2016 ranked as the 4th warmest summer season since records began in 1895. The statewide mean summer temperature of 76.6°F was 2.1°F above the 1981-2010 mean value of 74.5°F (Figure 1). Delaware’s four warmest summer seasons have all occurred since 2010.

Summer Precipitation

The statewide mean precipitation of 12.4 inches was 0.40 inches above the 1981-2010 normal of 12.0 inches, and was the 4th year in a row with above normal summer precipitation (Figure 2).

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) show that summer temperatures were above normal across the majority of the State, with northern New Castle County and Chester County, PA having the largest positive anomalies (Figure 3). The Wilmington/New Castle County Airport recorded 34 days of temperatures greater than or equal to 90°F, twice the normal number. Only two years, 2010 and 1988, had more 90°F summer days than 2016.

Summer precipitation varied significantly across the State depending upon location (Figure 4). The variable pattern of precipitation is due to the small-scale nature of convective storms; dropping heavy precipitation in some areas, while leaving others relatively dry.

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Warm green plants in the sun

Hot and Moist Conditions Prevail Across Delaware During July 2016

 
 

July Temperatures

Preliminary data indicates that the statewide average temperature in July was 79.6°F, 3.0°F above the 1981-2010 normal of 76.6°F (Figure 1). July 2016 was the 5th warmest July since records began in 1895.

July Precipitation

Delaware’s statewide precipitation for July 2016 averaged 4.92 inches, 0.78 inches above the 1981-2010 mean of 4.14 inches (Figure 2). Precipitation amounts varied widely across the State as convective storms hit some areas, but missed others.

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) show that temperatures were above normal across the entire State, with the largest temperature anomalies found across northern Sussex and southern Kent counties (Figure 3). Precipitation varied significantly across the First State, with the largest positive anomaly found in the Seaford area (Figure 4). Much of the heavy precipitation in the southwestern portion of the State occurred during a strong thunderstorm on July 13th when over 5.0 inches of rain fell in many locations.

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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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