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Shenandoah National Park in 2021: the fourth warmest year, with below-normal precipitation
The National Park Service's Mid-Atlantic Inventory and Monitoring Network measures ecosystem "vital signs" across the Mid-Atlantic region, and weather and climate is one of them. This is the network's summary of 2021 at Shenandoah National Park.
Weather versus climate
Weather is the short-term change in the atmosphere, over minutes to months: what is happening outside right now. Climate is what to expect from long-term patterns of 30 years or more. The brief's shorthand: climate is a hot summer you might expect, weather a warm rainy day you get. So the question for 2021 is how it compared with a "normal" year.
The numbers
The brief uses county-scale data averaged over the eight Virginia counties around the park (Albemarle, Augusta, Greene, Madison, Page, Rappahannock, Rockingham and Warren) for the period of record from 1895 to 2021, courtesy of NOAA's Climate at a Glance program. Individual stations may differ, and the park's high elevations may have had different weather from the county averages. The brief calls 2021 much warmer than average with below-normal precipitation: the fourth warmest year on record and the 41st driest. Ten months were warmer than the long-term average, and March, October and December each ran more than 4 °F above it.
| Month | Average temperature (°F) | Departure from average (°F) | Total precipitation (in.) | Departure from average (in.) |
|---|---|---|---|---|
| January | 34.8 | +2.9 | 2.00 | -0.85 |
| February | 34.4 | +0.4 | 3.43 | +0.96 |
| March | 46.5 | +4.2 | 1.75 | -1.55 |
| April | 54.0 | +1.9 | 3.42 | +0.16 |
| May | 61.0 | -0.5 | 1.99 | -1.98 |
| June | 70.8 | +1.6 | 4.05 | -0.07 |
| July | 75.2 | +2.1 | 2.67 | -1.43 |
| August | 75.2 | +3.7 | 6.59 | +2.54 |
| September | 67.1 | +1.8 | 5.83 | +2.23 |
| October | 60.8 | +6.5 | 4.33 | +0.96 |
| November | 43.2 | -0.6 | 1.10 | -1.77 |
| December | 44.1 | +9.5 | 0.33 | -2.59 |
| Year | 55.6 | +2.8 | 37.50 | -3.41 |
Departures compare 2021 with the long-term averages for 1895 to 2020. In all, 37.5 inches of precipitation fell, 3.4 inches less than the long-term average. August and September were the wettest months relative to their averages, and December the driest.
A long view
Over the period of record, annual average temperature has risen by about 0.17 °F per decade and annual total precipitation by about 0.42 inch per decade.
Annual average temperature and annual total precipitation for the counties around the park, 1895 to 2021; dashed lines show linear estimates of change. Figure from the National Park Service's page.
National Park Service scientists have also used models to estimate that by 2100 the park's annual average temperature will rise by 3.1 to 8.8 °F, from the best-case to the worst-case scenario, and that annual total precipitation will rise by 8 to 14 percent, as reported by Gonzalez and others in 2018.
Sources
- National Park Service, Mid-Atlantic Inventory and Monitoring Network, "2021 Weather In Review: Shenandoah National Park" (https://www.nps.gov/articles/000/2021-weather-in-review-shenandoah-national-park.htm); the sunrise photograph and the two seasonal ranking charts are left out; rewritten in hubnx's own words.