2021 Weather In Review: Allegheny Portage Railroad National Historic Site

Lemon House (NPS/Victoria Stauffenberg)

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 Allegheny Portage Railroad National Historic Site.

This brief provides county-scale weather data averaged from all of the counties surrounding the park, including data from 1895–2021 (i.e. period of record). These counties include Blair and Cambria counties, Pennsylvania. 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 and had above normal total precipitation. The year ended as the 4^th warmest and 27^th wettest on record. Data indicate that over the long term, annual average temperature and annual total precipitation have both increased (+0.10 °F per decade and +0.46 inches per decade, respectively).

Temperature

In total, 2021 was the 4^th warmest year ever recorded at the park. All of the seasons were warmer than normal (Figure 1). Ten months had higher than normal temperatures with March, October, and December all being more than 4.5 °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	28.2	+3.0
February	25.7	-0.9
March	40.2	+4.6
April	48.5	+1.9
May	55.8	-1.6
June	67.8	+2.3
July	70.4	+0.8
August	71.7	+3.8
September	63.2	+1.9
October	56.3	+6.1
November	37.7	-1.6
December	37.4	+8.1
2021	50.2	+2.4

Precipitation

It was an above-average year for total precipitation with a very wet summer season and a moderately dry winter (Figure 2). The year ended as the 27^th wettest on record for Blair and Cambria counties. In all, 45.94 inches of precipitation fell, about 4 inches more 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	1.93	-1.15
February	2.90	+0.27
March	3.00	-0.63
April	2.71	-0.90
May	5.22	+1.12
June	3.64	-0.67
July	4.14	-0.05
August	6.67	+3.00
September	7.59	+4.08
October	3.29	+0.17
November	1.27	-1.76
December	3.58	+0.55
2021	45.94	+4.04

Temperature and Precipitation Trends
(1895-2021)

Data for Blair and Cambria counties, PA indicate that annual average temperature has increased approximately +0.10 °F per decade and annual total precipitation has increased approximately +0.46 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 3.2–9.4 °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 Blair and Cambria counties, PA. Dashed lines represent linear estimates of change. Data are available at https://www.ncdc.noaa.gov/cag/county/time-series.

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.