Data Date: May

pink flowers

May 2023 – Cool and Dry Across Delaware

Posted on | by Dan Leathers

May Temperatures

Preliminary data indicates that the statewide average temperature in May was 62.1oF, which is 1.5oF below the 1991-2020 mean value of 63.6oF (Figure 1).  May 2023 temperature was in the “normal” range of observations since 1895.

May Precipitation

Delaware’s statewide precipitation for May 2023 averaged 2.22 inches, 1.36 inches below the 1991-2020 mean of 3.58 inches (Figure 2).  This month’s precipitation was in the bottom one-third of all observations since 1895.

Statewide Spatial Anomalies

Data from the Delaware Environmental Observing System (DEOS) show that temperature departures were uniformly negative across the entire state (Figure 3) with many locations seeing negative anomalies of more than 3oF.  Precipitation anomalies were negative across the majority of the state, with many stations in New Castle County recording negative departures of more than three inches (Figure 4).   

National Anomalies

Temperatures were generally above normal across the northwestern United States (Figure 5), while most of the eastern one-third of the country saw below normal temperatures (Figure 5).  Precipitation departures were negative across most of the eastern United States (Figure 6), while the High Plains and Florida saw positive precipitation departures. The 500 hPa height pattern for May shows a jet stream ridge covering most of the western two-thirds of North America, while much of the eastern one-third of the United States was covered by a jet stream trough, contributing to the temperature anomalies found across these regions (Figure 7).

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Pink flower protruding from water

May 2022 – Warm with Near Normal Precipitation Across Delaware

Posted on | by Dan Leathers

May Temperatures

Preliminary data indicates that the statewide average temperature in May was 65.2o F, which is 1.6o F above the 1991-2020 mean value of 63.6o F (Figure 1).  This made May of 2022 the 18th warmest since records began in 1895. 

May Precipitation

Delaware’s statewide precipitation for May 2022 averaged 3.97 inches, 0.39 inches above the 1991-2020 mean (Figure 2).  This month’s precipitation total was in the “normal” category based upon records dating back to 1895.

Statewide Spatial Anomalies

Data from the Delaware Environmental Observing System (DEOS) show that temperature departures were above normal across nearly the entire state, with the most concentrated area of warmth in northern New Castle County (Figure 3).  Precipitation varied across Delaware, with most of the northern one-half of the State seeing above normal rainfall and most of the southern one-half of the State seeing slightly below normal precipitation amounts (Figure 4). 

National Anomalies

Temperatures were above normal across most of the eastern one-half and southern tier of the United States, with many areas seeing positive departures of 5o – 7o F.  The northwest portion of the country saw below normal temperatures with many areas experiencing temperatures 3o  – 5o F below average (Figure 5).  Precipitation anomalies varied greatly across the country (Figure 6), with extremely dry conditions across the southwestern portion of the nation. The 500 hPa height pattern for May shows a jet stream ridge located over much of eastern North America and a jet stream trough over the northwest United States,  contributing to the temperature anomalies across those regions (Figure 7).

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May 2021 – Mild and Dry Across Delaware

Posted on | by Dan Leathers

 

May Temperatures

Preliminary data indicates that the statewide average temperature in May was 64.0° F, which is 1.3° F above the 1981-2010 mean value of 62.7° F (Figure 1).  The statewide temperature in May 2021 fell within the top one-third of May observations since 1895.

May Precipitation

Delaware’s statewide precipitation for May 2021 averaged 2.90 inches, 0.96 inches below the 1981-2010 mean (Figure 2).  This placed this month’s precipitation total in the middle one-third of all years since 1895.

Statewide Spatial Anomalies

Data from the Delaware Environmental Observing System (DEOS) shows that temperature departures were generally small and varied from station to station across the State (Figure 3).  Precipitation was below normal at all stations throughout the State, however, none of the precipitation anomalies were large (Figure 4).

National Anomalies

Temperatures were generally below normal across much of the eastern United States except for New England.  Warmer than normal temperatures were found across California and much of the Southwest United States (Figure 5).  Precipitation anomalies varied greatly across the country with dry conditions continuing in the Southwest.  Portions of the Gulf Coast, from Louisiana to Texas, saw much above normal precipitation (Figure 6).  The 500 hPa height pattern for May shows no strong jet stream anomalies across the country (Figure 7), leading to the relatively mild temperature anomalies for the month.

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Dry cracked white ground

May 2020 – Cool and Dry Across Delaware

Posted on | by Dan Leathers

May Temperatures

Preliminary data indicates that the statewide average temperature in May was 60.8° F, which is 1.9° F below the 1981-2010 mean value of 62.7° F (Figure 1).  May 2020 continued our cool spring temperatures that began in April.

May Precipitation

Delaware’s statewide precipitation for May 2020 averaged 2.64 inches, 1.22 inches below the 1981-2010 mean (Figure 2).  This placed the May 2020 precipitation amount in the “normal” category for all years since 1895.

Statewide Spatial Anomalies

Data from the Delaware Environmental Observing System (DEOS) show that temperature departures were uniformly below normal throughout the State (Figure 3), with most stations between 2° and  4° F below the 30-year mean.  Precipitation was below normal at almost all locations, with negative anomalies of between one and two inches across all three Delaware Counties (Figure 4).

National Anomalies

Temperatures were below normal across most of the eastern two-thirds of the U.S.  Departures were generally between 1° to 5° F below normal across this area.  Positive temperature anomalies were found across much of the western and southwestern portions of the United States (Figure 5).  Precipitation varied greatly across the country, with little to no precipitation falling across the southwest while an area of very heavy precipitation was found across the Carolinas.  This area of heavy precipitation was associated with Tropical Storms Arthur and Bertha (Figure 6).  The 500 hPa height pattern for May showed a weak trough dominating the eastern one-half of the country (Figure 7) leading to the cooler temperatures across our region.

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Spring 2019 – Warm Temperatures and Near Normal Precipitation Across Delaware

Posted on | by Dan Leathers

Spring Temperatures

Spring Temperatures Preliminary data indicates that spring temperatures averaged 55.8°F, 2.4°F above the 30-year “normal” of 53.4°F (Figure 1). Spring 2019 is tied with 1945 and 2011 as the 7th warmest since records began in 1895.

Spring Precipitation

Spring Precipitation The statewide mean precipitation of 12.10 inches was 0.4 inches above the 1981-2010 normal of 11.70 inches (Figure 2). This value placed the spring of 2019 in the wettest one-third of years since 1895.

Statewide Spatial Averages

Statewide Spatial Anomalies Data from the Delaware Environmental Observing System (DEOS) show that spring temperature anomalies were above normal across the entire State (Figure 3). Spring precipitation anomalies varied significantly across the state, but were all above normal (Figure 4). Anomalies were greater than three inches at several of the DEOS stations.

National Anomalies

National Anomalies Above normal spring temperatures were found across the southern Atlantic coast of the U.S. from Florida through the Mid-Atlantic Region (Figure 5), while colder than normal temperatures were found across the north-central portions of the country. Precipitation varied greatly across the continental United States, with the Mid-Atlantic Region generally seeing above normal values (Figure 6).

Positive 500 hPa height anomalies were present over the Mid-Atlantic Region during the spring season, indicative of anomalous ridging with enhanced flow from the south and moisture transport into our State (Figure 7). This anomalous flow helped to make the season warmer and wetter than normal.

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May 2019 – Very Warm Temperatures and Above Normal Precipitation Across Delaware

Posted on | by Dan Leathers

May Temperatures

Preliminary data indicates that the statewide average temperature in May was 66.6°F, which is 3.9°F above the 1981-2010 mean value of 62.7°F (Figure 1). This places May 2019 as the 7th warmest since records began in 1895, tied with the years 1896 and 1944 in that position.

May Precipitation

Delaware’s statewide precipitation for May 2019 averaged 4.92 inches, 1.06 inches above the 1981-2010 mean (Figure 2). Delaware’s May precipitation was in the top 0ne-third of values for the last 125 years.

Statewide Spatial Anomalies

Data from the Delaware Environmental Observing System (DEOS) show that temperature departures were uniformly above normal across the entire state (Figure 3), with some stations seeing anomalies of greater than 3.0°F. Precipitation departures were generally above normal across the state (Figure 4) with the largest positive precipitation anomalies found across northern New Castle County.

National Anomalies

The United States saw both positive and negative temperature anomalies during May, with the Southeast, mid-Atlantic and the Pacific Northwest seeing above normal temperatures (Figure 5). Wet conditions were prevalent across the Great Plains, California and parts of the Southwest, while the Southeast was quite dry (Figure 6).

The 500 hPa height pattern for May showed anomalous ridging of the jet stream over our region leading to enhanced southerly flow and higher than normal temperatures (Figure 7).

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Rain drops on a window

Delaware Experiences Very Warm and Wet Conditions in May 2018

Posted on | by Dan Leathers

 

 

 

May Temperatures

Nearly the entire United States experienced warmer than normal conditions during May 2018, with some locations in the Midwest seeing temperatures 7°F to 10°F above normal (Figure 1). For Delaware, preliminary data indicates that the statewide average temperature in May was 67.8°F, which is 5.1°F above the 1981-2010 mean value of 62.7°F (Figure 2). This made May 2018 the fourth warmest on record since 1895. In addition, May 2018 was 16.7°F warmer than May, signaling an abrupt transition from the cold to warm season.

May Precipitation

Delaware’s statewide precipitation for May 2018 of 7.18 inches was the fourth wettest since records began in 1895 (Figure 3). This May’s precipitation total was 3.32 inches above average for the month. The first five months of 2018 have been the 13th wettest since records began in 1895, with a total precipitation anomaly of nearly 5 inches for the year.

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) show that temperature departures were above normal across the entire State (Figure 4), with several stations recording anomalies of greater than 5o F. Precipitation anomalies were above normal across the entire State as well (Figure 5), with the largest anomalies found across southern Kent and Sussex Counties.

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Bright yellow flowers contrast a bright blue sky

Near Normal Temperatures and Above Normal Precipitation Characterize the 2018 Spring Season Across Delaware

Posted on | by Dan Leathers

 

 

Spring Temperatures

Preliminary data indicates that spring temperatures were exactly equal to the 30-year “normal” of 53.4°F (Figure 1). This was the fourth year in a row with spring temperatures at or above the 30-year mean.

Spring Precipitation

The statewide mean precipitation of 14.48 inches was 2.78 inches above the 1981-2010 normal of 11.70 inches, making it the 15th wettest since records began in 1895 (Figure 2).

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) show that spring temperature anomalies across the State varied dependent upon location and were generally small at all stations (Figure 3). Spring precipitation totals were above normal across most of the State, with the largest positive anomalies found across Sussex County (Figure 4), where some stations recorded spring precipitation amounts more than six inches above average.

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White flowers on a branch

May 2017: Above Normal Precipitation with Near Normal Temperatures

Posted on | by Dan Leathers

 

 

May Temperatures

Preliminary data indicates that the statewide average temperature in May was 62.8°F; this was 0.1°F above the 1981-2010 normal of 62.7°F (Figure 1).

May Precipitation

Delaware’s statewide precipitation for May 2017 averaged 5.92 inches, 2.06 inches above the 1981-2010 mean (Figure 2). May 2017 was only the second of the last eight months with above normal precipitation across the First State.

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) shows that temperatures varied greatly across the State, with large, negative temperature anomalies found in western New Castle and northern Kent Counties (Figure 3). Precipitation was above average at all sites statewide, with the largest positive anomalies across central Delaware (Figure 4).

 

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Wet pink flowers in green grass

Warm and Moist Conditions Characterize the 2017 Spring Season Across Delaware

Posted on | by Dan Leathers

 
 

Spring Temperatures

Preliminary data indicates that spring temperatures were above the 30-year “normal”. The statewide mean spring temperature of 55.4°F was 2.0°F above the 1981-2010 mean value of 53.4°F (Figure 1). Spring 2017 was tied with 2002 as the 10th warmest since records began in 1895.

Spring Precipitation

The statewide mean precipitation of 13.00 inches was 1.30 inches above the 1981-2010 normal of 11.70 inches, putting it in the top 25 wettest since records began in 1895 (Figure 2).

Statewide Spatial Averages

Data from the Delaware Environmental Observing System (DEOS) show that spring temperatures across the State were above normal at most locations, with the largest positive anomalies found across inland Sussex County (Figure 3).

Spring precipitation totals were quite varied across the State with positive anomalies found across northern Kent and southern New Castle Counties, while significant below normal anomalies were found in portions of Chester County, PA (Figure 4).

 

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