Last updated: May 13, 2021
Article
2020 Weather in Review: Assateague Island National Seashore
NPS/Baranowski
Weather and climate play significant roles in driving both physical and ecological processes. For example, the active processes that shape the North Atlantic coastline are largely the result of meteorological events such as wind-driven waves. For research and long-term ecological monitoring, weather and climate data provide the potential for correlations to be made with observed physical and ecological pattern data.
This resource brief provides a summary of both historic and current (2020) weather data for Assateague Island National Seashore (ASIS), Maryland (MD). Information in this brief represents county-scale weather data averaged from the county surrounding the park, Worchester County, MD. Because tide levels and wind can be significant for coastal parks, the annual water level and wind data are included. Individual weather station data may vary from what is reported here. Data are available from the National Climate Data Center.
Temperature
Overall, 2020 was the 2nd warmest year on record with an average temperature of 59.4 °F — 3.1 degrees above average (Figure 1). Spring nearly reached “above normal” temperatures, while summer, autumn, and winter seasons fell within “much above normal” temperatures. 2020 had the 2nd warmest winter on record. The warmest month was July with an average of 81 degrees — 4.7 degrees over the monthly average. Every month had higher than average temperatures, except May at 1.4 degrees below average (Table 1).
| Month (2020) | Average temperature (°F) | Departure from long-term average temperature (°F) |
|---|---|---|
| January | 43.0 | +6.8 |
| February | 43.6 | +6.7 |
| March | 50.5 | +6.3 |
| April | 53.6 | +0.5 |
| May | 61.4 | -1.4 |
| June | 73.5 | +2.1 |
| July | 81.0 | +4.7 |
| August | 78.3 | +3.2 |
| September | 70.1 | +0.9 |
| October | 62.4 | +3.7 |
| November | 53.8 | +5.6 |
| December | 42.2 | +2.8 |
| Annual | 59.4 | +3.1 |
Precipitation
Overall, 2020 was the 12th wettest year on record with a total of 54.57 inches of precipitation (Figure 2, Table 2). Seasonally, winter and summer fell within “above normal” levels, spring fell to a “below normal” level, while summer reached a “much above normal” level. Eight months had higher than average amount of precipitation. August had the greatest amount of precipitation in 2020 at 7.52 inches — 2.92 inches over the average monthly rainfall. May had the lowest amount at 1.9 inches — 1.43 inches below average.
| Month (2020) | Total precipitation (in) | Departure from long-term average precipitation (in) |
|---|---|---|
| January | 3.34 | -0.14 |
| February | 4.42 | +1.07 |
| March | 3.78 | -0.25 |
| April | 3.35 | +0.02 |
| May | 1.90 | -1.43 |
| June | 2.22 | -1.34 |
| July | 5.67 | +1.42 |
| August | 7.52 | +2.92 |
| September | 3.93 | +0.30 |
| October | 5.41 | +1.97 |
| November | 5.73 | +2.75 |
| December | 7.20 | +3.74 |
| Annual | 54.47 | +11.03 |
Temperature and Precipitation Trends (1895–2020)
Temperature and precipitation data are gathered from the U.S. Climate Divisional Database, which stores data from January 1895 to the present, and can be accessed via the National Oceanic and Atmospheric Administration’s (NOAA) National Centers for Environmental Information (NCEI) website (Figure 3). Users can choose different geographic scales (i.e., global, national, statewide), different temporal scales, and display them in various types of graphical formats. Temperature and precipitation data presented in this brief are for Worcester County, MD.
Wind
Wind data (wind speed and direction) is collected from the NOAA National Water Level Observation Network (NWLON) station 8570283 located at the inlet of Ocean City, MD. Each direction is divided up into categories called bins that are color coated to represent the frequency of a certain wind speed. The length of the bin represents the number of times wind comes from a given direction as well as the speed of the wind. The longer the length of the bin, the more frequent the given speed was recorded (Figure 4).
Tide Levels
Water level data is also collected from the NOAA NWLON station 8570283 in the vicinity of the inlet at the northern end of the island. Located at the inlet of Ocean City, MD, this station has records dating back to 1978. The data is graphed to show the difference in the predicted tide level verses what was observed (Figure 5). The offsets in height reflect the effect from storm surge on the normal, astronomically driven tide level.
