Weather without surprises: Castle Shannon keeps close to the norm for U.S. towns
The warmest part of a July day comes in at 83° on average. June is the wettest month, February the driest. By July afternoons alone, it runs cooler than 70% of U.S. towns. The frost-free window for a garden runs roughly April 18 to October 28.
A year in Castle Shannon at a glance
Each month’s typical high and low, and what it brings.
What stands out about Castle Shannon’s climate
Compared with towns across the U.S., with Castle Shannon’s place in Pennsylvania beside it.
What a year in Castle Shannon feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 193 frost-free days a year
In half of years the last 32° night comes by April 18 and the first by October 28. Frost and day counts come from NOAA’s station at Pittsburgh Allegheny Co Airport, 5 miles from the town’s center, at about the same height.
The 2023 USDA map puts Castle Shannon’s center in zone 6b: the coldest night of a typical winter, averaged over 1991–2020, reaches about −1°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
About 44 inches of snow a winter
Snow, measured at Pittsburgh International Airport, falls mostly in January. Precipitation (rain plus melted snow) adds up to 42 inches a year; June is the wettest month and February the driest. Rain or snow falls on about 154 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Castle Shannon
87% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from October through April.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Pittsburgh Allegheny Co Airport.
Living with Castle Shannon’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
193 frost-free days in zone 6b. The last frost comes by Apr 18 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Oct 28.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August, September and October. 0.7 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Castle Shannon from natural hazards, river flooding is the largest share (72%); heat waves, cold waves, winter storms and ice storms together are 19%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Castle Shannon and its neighbors
Pittsburgh the hottest July afternoons (85°, 2° warmer). Differences under a degree are within what the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Castle Shannon’s, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| Castle Shannon, PA | 21° | 83° | 42" | 44" |
| East Chicago, IN | 19° | 83° | 38" | 39" |
| Walden, NY | 18° | 84° | 44" | 44" |
| Bluefield, WV | 23° | 81° | 42" | 40" |
| Chicago, IL | 18° | 84° | 38" | 39" |
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value. Snow and frost-free days come from the nearest weather station, so neighbors often share them.
Warmer than it used to be
The last 30 years in Castle Shannon averaged 1.2° warmer than the 1900s. The biggest change is in December (+2.4°).
A smaller shift than in 66% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods.
How Castle Shannon compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Castle Shannon’s place among Pennsylvania’s.
Castle Shannon weather by month
Highs, lows and precipitation from NOAA’s grid at Castle Shannon’s center; snow, wet days and snow on the ground from Pittsburgh International Airport. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 37° | 21° | 3.0" | 13.3" | 17 | 14 | 21° – 39° |
| February | 40° | 23° | 2.6" | 11.7" | 14 | 11 | 19° – 41° |
| March | 50° | 31° | 3.3" | 7.6" | 14 | 5 | 34° – 51° |
| April | 63° | 40° | 3.5" | 1.0" | 14 | 0 | 45° – 56° |
| May | 72° | 49° | 4.1" | 0.0" | 14 | 0 | 54° – 68° |
| June | 80° | 58° | 4.4" | 0.0" | 12 | 0 | 65° – 71° |
| July | 83° | 62° | 4.3" | 0.0" | 11 | 0 | 68° – 77° |
| August | 82° | 61° | 3.8" | 0.0" | 11 | 0 | 67° – 76° |
| September | 76° | 54° | 3.5" | 0.0" | 10 | 0 | 61° – 69° |
| October | 64° | 43° | 3.0" | 0.4" | 11 | 0 | 50° – 60° |
| November | 52° | 34° | 2.9" | 2.4" | 12 | 1 | 37° – 48° |
| December | 41° | 26° | 3.2" | 7.7" | 15 | 8 | 23° – 45° |
| Year | 62° | 42° | 41.6" | 44.1" | 154 | 40 |
How much a month can swing
A normal is an average. February swings the most: from 1991 to 2020 its average ranged from 19° to 41°. June is the most reliable, staying within 7°.
Where Castle Shannon’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Castle Shannon’s center.
- Snow: Pittsburgh International Airport.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Pittsburgh Allegheny Co Airport, 5 miles from the town’s center, at about the same height; the nearest station that passes our checks for distance, height and agreement with the grid.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Castle Shannon’s climate
What is the weather like in Castle Shannon?
A typical July afternoon reaches 83°, a January night drops to 21°, and about 44 inches of snow falls in a normal winter. Colder January nights than 54% of U.S. towns; cooler July afternoons than 70% of U.S. towns.
How cold does it get in Castle Shannon in winter?
January nights average 21°. About 106 nights a year reach 32° or below and 1 reach 0° or below. In the coldest January of the last 30 years the month averaged 21°.
How much snow does Castle Shannon get?
About 44 inches in a normal winter at Pittsburgh International Airport, most of it in January, with snow on the ground about 40 days a year.
How hot does it get in Castle Shannon?
July, with a typical high of 83° and a low of 62°. About 8 days a year reach 90° (Pittsburgh Allegheny Co Airport).
When is the first and last frost in Castle Shannon?
In half of years the last spring frost (32°) comes by April 18 and the first fall frost by October 28, about 193 frost-free days, at Pittsburgh Allegheny Co Airport.
What growing zone is Castle Shannon in?
Zone 6b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −1°.
What is the best time of year to visit Castle Shannon?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, July, August, September and October. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Castle Shannon getting warmer?
Yes: 1991–2020 averaged 1.2° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 66% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Castle Shannon.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.