Mount Gretna, PA climate
Mount Gretna has chilly winters and warm summers. A typical July afternoon reaches 84°, a January night drops to 21°, and about 24 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Mount Gretna feels like
Winter
Spring
Summer
Fall
Mount Gretna weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 37° | 21° | 3.3" | 6.8" | 10 | 9 | 19° – 37° |
| February | 41° | 23° | 2.7" | 7.8" | 9 | 9 | 20° – 40° |
| March | 50° | 30° | 3.9" | 4.2" | 11 | 3 | 34° – 50° |
| April | 62° | 40° | 3.8" | 0.4" | 12 | 0 | 47° – 56° |
| May | 72° | 50° | 4.0" | 0 | 13 | 0 | 57° – 67° |
| June | 80° | 59° | 4.4" | 0 | 11 | 0 | 66° – 73° |
| July | 84° | 64° | 4.6" | 0 | 11 | 0 | 70° – 78° |
| August | 83° | 62° | 4.3" | 0 | 10 | 0 | 68° – 76° |
| September | 76° | 55° | 4.8" | 0 | 10 | 0 | 62° – 69° |
| October | 64° | 44° | 4.3" | 0.3" | 10 | 0 | 49° – 61° |
| November | 53° | 34° | 3.3" | 0.5" | 9 | 0 | 38° – 48° |
| December | 42° | 26° | 3.7" | 4.0" | 10 | 4 | 25° – 45° |
| Year | 62° | 42° | 46.9" | 24.0" | 125 | 26 |
“Wet days” have at least 0.01" of rain or melted snow. “Snow on ground” counts days with 1" or more. The 30-year range is the coldest and warmest that month’s average temperature got between 1991 and 2020.
Rain and snow in Mount Gretna
Mount Gretna gets 47 inches of rain and melted snow a year. September is the wettest month and February the driest. Rain or snow falls on about 125 days a year. Snow covers the ground about 26 days of the year.
About 185 frost-free days a year
In half of years the last 32° night comes by April 20 and the first one by October 25. That leaves about 185 frost-free days for gardens, longer than 58% of U.S. towns.
Heating and cooling a home in Mount Gretna
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Mount Gretna, 86% of that work is heating and 14% is cooling, so the furnace matters far more than the air conditioner.
Degree days measure how far each day’s average temperature falls below or rises above 65°, added up over a year. Source: NOAA station normals.
Mount Gretna and its neighbors
Mount Gretna borders 2 towns with climate data. January nights across them vary by 0.6°. West Cornwall has the coldest January nights (21°) and South Londonderry the hottest July afternoons (85°). Mount Gretna’s January low is 21° and its July high 84°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How Mount Gretna compares
Compared with every U.S. town and city on TownTapestry, each counted once.
Warmer than it used to be
The last 30 years in Mount Gretna averaged 1.8° warmer than the 1900s. The biggest change is in December (+3.3°). The shift is larger than in 89% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Mount Gretna’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. December swings the most: between 1991 and 2020 its average temperature ranged from 25° to 45°. June is the most reliable, staying within 7°.
Common questions about Mount Gretna’s climate
What is the coldest month in Mount Gretna?
January, with a typical high of 37° and a low of 21°.
What is the hottest month in Mount Gretna?
July, with a typical high of 84° and a low of 64°. About 13 days a year reach 90°.
How much snow does Mount Gretna get?
About 24 inches in a normal winter, most of it in February.
When is the first frost in Mount Gretna?
In half of years the first 32° night comes by October 25, and the last spring frost by April 20.
What is the rainiest month in Mount Gretna?
September, with 4.8 inches of rain and melted snow. The year totals 47 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Mount Gretna itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Lebanon 2 W, PA (6 mi) away. Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.