2020 Weather In Review: Johnstown Flood National Memorial

NPS / N. Lewis

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 2020 weather conditions at Johnstown Flood National Memorial.

This brief provides county-scale weather data from Cambria County, PA, including data from 1895–2020 (i.e. period of record). Individual weather station data may vary from what is reported here. Data are available from the National Climate Data Center.

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 2020 weather placed in the context of long-term climate (i.e. how did 2020 compare to a "normal" year?).

2020 Summary

In all, 2020 was very warm but had near-normal precipitation. The year ended as the 5th warmest and 58th driest on record. Weather data collected from surrounding areas shows that annual average temperature and annual total precipitation have both increased over the last century (+0.08 °F per decade and +0.45 inches per decade, respectively).

Temperature

In total, 2020 was the 5^th warmest year ever recorded at the park. All of the seasons were very warm except the spring, which was unusually cold (Figure 1). Nine months had higher than normal temperatures with January, February, and March all being more than 6.2 °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.

Month/Year	Average temperature (°F)	Departure from long-term average (°F)
January	30.6	+6.2
February	32.0	+6.2
March	41.1	+6.3
April	43.2	-2.6
May	53.8	-2.9
June	65.9	+1.2
July	73.0	+4.3
August	69.6	+2.6
September	59.7	-0.8
October	50.2	+0.7
November	43.1	+4.6
December	29.7	+1.2
2020	49.3	+2.2

_{Table 1. Monthly and annual average temperature and departure from long-term averages. Departures from average show how different 2020 was compared to relevant averages from 1895-2019.}

Precipitation

In total, it was a near-normal year for precipitation, but it was highly variable across seasons (Figure 2). The year ended as the 58^th driest on record. In all, 43.1 inches of precipitation fell, about 1 inch 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.

Month/Year	Total precipitation (in.)	Departure from long-term average (in.)
January	3.8	+0.5
February	4.3	+1.4
March	5.6	+1.8
April	5.6	+1.9
May	3.1	-1.1
June	2.2	-2.4
July	3.1	-1.3
August	3.6	-0.2
September	2.3	-1.3
October	3.4	+0.2
November	2.9	-0.3
December	3.2	0.0
2020	43.1	-0.8

_{Table 2. Monthly and annual total precipitation and departure from long-term averages. Departures from average show how different 2020 was compared to relevant averages from 1895-2019.}

Temperature and Precipitation Trends
(1895-2020)

Data for Cambria County, PA indicate that annual average temperature has increased approximately +0.08 °F per decade and annual total precipitation has increased approximately +0.45 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 1895–2020 for Cambria 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.