Allegheny Portage Railroad National Historic SitePage 8 of 20
Allegheny Portage Railroad National Historic Site in 2021: a very warm year
In 2021 the area around Allegheny Portage Railroad National Historic Site, in Pennsylvania, was very warm and had above-normal total precipitation. The year ended as the 4th warmest and 27th wettest on record. Over the long term, both annual average temperature and annual total precipitation have increased.
Lemon House. NPS photo.
Where the numbers come from
The Eastern Rivers and Mountains Network measures ecosystem "vital signs" in selected national parks in West Virginia, Pennsylvania, New Jersey and New York, and weather and climate is one of them. This summary uses county-scale data averaged over the counties around the park, Blair and Cambria counties in Pennsylvania, for 1895 to 2021 (the period of record). The data and analyses come from NOAA's Climate at a Glance program.
The page also explains the difference between weather and climate. Weather is short-term (minutes to months) change in the atmosphere, what is happening outside at this very moment. Climate is what one expects from long-term patterns over 30 years or more: climate is what you might expect, like a hot summer, and weather is what you get, like a warm rainy day.
Temperature
In total, 2021 was the 4th warmest year on record for the park's counties, with an annual average of 50.2 °F, 2.4 °F above the long-term average. December (+8.1 °F) and October (+6.1 °F) stood out; February, May and November were slightly below average.
| Month or 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 |
Departures show how 2021 differed from the averages for 1895 to 2020.
Precipitation
It was an above-average year for total precipitation: the 27th wettest on record for Blair and Cambria counties. In all, 45.94 inches fell, about 4 inches more than the long-term average. August and September were the wettest months relative to normal.
| Month or 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 |
The long-term trend, 1895 to 2021
For Blair and Cambria counties, annual average temperature has risen by about 0.10 °F per decade and annual total precipitation by about 0.46 inches per decade since 1895.
Annual average temperature (°F) and annual total precipitation (in.), 1895 to 2021, Blair and Cambria counties. Dashed lines show linear estimates of change. Chart from the National Park Service's page.
National Park Service scientists have also looked ahead. Models estimate that by 2100 the park's annual average temperature will rise by 3.2 to 9.4 °F, from the best-case to the worst-case scenario, and annual total precipitation by 6 to 12 percent; the page points to a 2018 paper by Gonzalez and colleagues for details.
Sources
- National Park Service, Eastern Rivers and Mountains Network, "2021 Weather In Review: Allegheny Portage Railroad National Historic Site" (https://www.nps.gov/articles/000/2021-weather-in-review-allegheny-portage-railroad-national-historic-site.htm), published as a work of the United States government; the page's seasonal ranking charts and seasonal statements, and its count of warm months, are left out because they do not agree with its monthly tables; rewritten in hubnx's own words.