2021 Weather In Review: Flight 93 National Memorial

The Allee at Memorial Plaza

NPS Photo/C.Claycomb

In order to better understand ecosystem health in national parks, the Eastern Rivers and Mountains Network measures ecosystem "vital signs" in select national parks in West Virginia, Pennsylvania, New Jersey, and New York. One of those vital signs is weather and climate. Below is a summary of 2021 weather conditions at Flight 93 National Memorial.

This brief provides county-scale weather data from Somerset County, PA, including data from 1895–2021 (i.e. period of record). Data and analyses herein are courtesy of the National Oceanic and Atmospheric Administration's (NOAA) Climate at a Glance Program.

Weather vs. Climate

First of all, what is the difference between weather and climate? Weather consists of the short-term (minutes to months) changes in the atmosphere. Weather is what is happening outside at this very moment, be it rain, snow, or just a warm sunny day. Climate is what you expect to see based on long-term patterns of over 30 years or more. An easy way to remember the difference is that climate is what you might expect, like a hot summer, and weather is what you get, like a warm rainy day.

The following information includes a discussion of 2021 weather placed in the context of long-term climate (i.e. how did 2021 compare to a "normal" year?).

2021 Summary

In all, 2021 was very warm but had near-normal total precipitation. The year ended as the 7^th warmest and 63^rd wettest on record. Data indicate that over the long term, annual average temperature and annual total precipitation have both increased (+0.09 °F per decade and +0.43 inches per decade, respectively).

Temperature

In total, 2021 was the 7^th warmest year ever recorded at the park. All of the seasons were warmer than average except the spring, which was closer to normal (Figure 1). Nine months had higher than normal temperatures with March, August, October, and December all being at least 4 °F above long-term averages (Table 1).

Figure 1. Seasonal and annual temperature rankings for counties surrounding the park. An arrow at the top of the figure would represent the warmest year/season on record (since 1895); at the bottom, the coldest year/season on record.

_{Table 1. Monthly and annual average temperature and departure from long-term averages. Departures from average show how different 2021 was compared to relevant averages from 1895-2020.}

Month/Year	Average temperature (°F)	Departure from long-term average (°F)
January	27.6	+2.6
February	25.8	-0.7
March	40.0	+4.6
April	47.8	+1.7
May	55.0	-1.6
June	66.1	+1.6
July	69.2	+0.9
August	70.6	+4.0
September	62.1	+1.7
October	55.7	+6.2
November	37.4	-1.1
December	37.5	+8.8
2021	49.6	+2.4

Precipitation

It was a near-normal year for total precipitation in Somerset County, PA, though the summer was very wet and the spring and autumn were relatively dry. In all, 2021 ranked as the 63^rd wettest on record (Figure 2). In total, 44.13 inches of precipitation fell, just 0.13 inches less than the long-term average (Table 2).

Figure 2. Seasonal and annual precipitation rankings for counties surrounding the park. An arrow at the top of the figure would represent the wettest year/season on record (since 1895); at the bottom, the driest year/season on record.

_{Table 2. Monthly and annual total precipitation and departure from long-term averages. Departures from average show how different 2021 was compared to relevant averages from 1895-2020.}

Month/Year	Total precipitation (in.)	Departure from long-term average (in.)
January	2.02	-1.47
February	3.02	+0.07
March	3.63	-0.30
April	3.23	-0.56
May	5.35	+1.10
June	3.27	-1.31
July	4.39	+0.06
August	5.18	+1.16
September	6.71	+3.24
October	2.94	-0.19
November	0.93	-2.09
December	3.46	+0.15
2021	44.13	-0.13

Temperature and Precipitation Trends
(1895-2021)

Data for Somerset County, PA indicate that annual average temperature has increased approximately +0.09 °F per decade and annual total precipitation has increased approximately +0.43 inches per decade since 1895 (Figure 3).

National Park Service scientists have forecast future changes in climate too. Models estimate that by 2100, annual average temperature at the park will increase by 3.1–9.2 °F (from a best-case to worst-case scenario, respectively). Annual total precipitation is expected to increase by 6–12% (see Gonzalez et al., 2018 for details).

Figure 3. Annual average temperature (°F) and annual total precipitation (in.) from 1895–2021 for Somerset County, PA. Dashed lines represent linear estimates of change.

Climate Change

Today's rapid climate change challenges national parks in ways we've never seen before. Wildlife migrations are altered, increasingly destructive storms threaten cultural resources and park facilities, habitat is disrupted—the list goes on. Go to the NPS Climate Change site to discover how climate change is affecting our nation's treasures, what the National Park Service is doing about it, and how you can help.

For more information, contact Mid-Atlantic Network Biologist, Jeb Wofford or Eastern Rivers and Mountains Network Program Manager, Matt Marshall.