West Mifflin, Pennsylvania climate: Normal weather by month, frost dates and records
West Mifflin's normal year runs from 22°F January nights to 83°F July afternoons, with 41.3 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 11.3°C, January lows of −5°C, July highs of 28°C, 1,050 mm of precipitation a year.
- NOAA stationPittsburgh Allegheny County Airport
- Station IDUSW00014762
- Location40.35°N 79.92°W
- Elevation1,248 ft (380 m)
- From the centerunder 1 mile
- Population18,902
On October 14, the normal high in West Mifflin is 64°F and the normal low 46°F, and the chance of measurable rain or snow is 45%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for West Mifflin.
- Jan 37° 22°
- Feb 40° 24°
- Mar 49° 31°
- Apr 63° 42°
- May 72° 52°
- Jun 79° 60°
- Jul 83° 64°
- Aug 81° 63°
- Sep 75° 56°
- Oct 63° 45°
- Nov 51° 35°
- Dec 41° 28°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in West Mifflin each month?
July is the warmest month, with normal highs of 83°F; January the coldest, with normal lows of 22°F. The most precipitation falls in June (4.58 in), the least in February (2.57 in).
Each month has its own page with the day-by-day normals, the month's records and its recent years:
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 37°F | 22°F | 29.5°F | 3.08 | 13 | <1 | 25 | 9 h 40 min |
| February | 40°F | 24°F | 32.1°F | 2.57 | 13 | <1 | 23 | 10 h 40 min |
| March | 49°F | 31°F | 40.4°F | 3.22 | 14 | <1 | 17 | 11 h 50 min |
| April | 63°F | 42°F | 52.1°F | 3.40 | 14 | <1 | 5 | 13 h 10 min |
| May | 72°F | 52°F | 61.8°F | 4.08 | 15 | <1 | <1 | 14 h 20 min |
| June | 79°F | 60°F | 69.5°F | 4.58 | 14 | 1 | <1 | 15 h |
| July | 83°F | 64°F | 73.6°F | 3.93 | 13 | 4 | <1 | 14 h 50 min |
| August | 81°F | 63°F | 72.1°F | 3.81 | 12 | 3 | <1 | 13 h 50 min |
| September | 75°F | 56°F | 65.4°F | 3.54 | 12 | 1 | <1 | 12 h 30 min |
| October | 63°F | 45°F | 54.2°F | 3.06 | 14 | <1 | 2 | 11 h 10 min |
| November | 51°F | 35°F | 43.2°F | 3.03 | 12 | <1 | 12 | 10 h |
| December | 41°F | 28°F | 34.4°F | 3.04 | 14 | <1 | 23 | 9 h 20 min |
| Year (annual) | 61°F | 44°F | 52.4°F | 41.34 | 161 | 8 | 106 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 3°C | −5°C | −1.4°C | 78 mm |
| February | 4°C | −4°C | 0.1°C | 65 mm |
| March | 10°C | 0°C | 4.7°C | 82 mm |
| April | 17°C | 5°C | 11.2°C | 86 mm |
| May | 22°C | 11°C | 16.6°C | 104 mm |
| June | 26°C | 16°C | 20.8°C | 116 mm |
| July | 28°C | 18°C | 23.1°C | 100 mm |
| August | 27°C | 17°C | 22.3°C | 97 mm |
| September | 24°C | 13°C | 18.6°C | 90 mm |
| October | 17°C | 7°C | 12.3°C | 78 mm |
| November | 11°C | 2°C | 6.2°C | 77 mm |
| December | 5°C | −2°C | 1.3°C | 77 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Murrysville (11 miles away), gets 25 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USW00014762; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit West Mifflin?
Normal highs sit between 65°F and 85°F in May, June, July, August and September. Of those, September has the fewest days with rain (12).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USW00014762.
When is the last frost in West Mifflin?
In West Mifflin, the last spring frost (32°F) comes after April 18 in half of years and after May 6 in one year in ten; the first autumn frost comes before October 28 in half of years and before October 14 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- April 181 year in 10 after May 6; 9 in 10 after April 2
- First autumn frost, half of years before
- October 281 year in 10 before October 14; 9 in 10 before November 10
NOAA puts the median frost-free season at 193 days, and the season without a hard freeze (28°F) at 216 days.
A hard freeze (28°F) comes after April 5 in half of springs and before November 8 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts West Mifflin in zone 6b in ZIP code 15122. By the map's own method, the average of each year's coldest night over 1991-2020, West Mifflin's NOAA station is in zone 7a: the coldest night of a typical year reaches 1°F (21 complete years); the map interpolates between stations and terrain, so the station and the ZIP area can differ by half a zone.
Frost dates for every NOAA station in Pennsylvania · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USW00014762; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
How hot and how cold does it get in West Mifflin?
In a normal year in West Mifflin, 8 days a year reach 90°F, 106 nights fall to 32°F or colder and 161 days bring measurable precipitation.
- Days at 90°F or more
- 8a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 106a normal year
- Days that stay below freezing
- 33high of 32°F or less
- Days with 0.01 inch of precipitation
- 161a normal year
The highest temperature in this station's record (since 1935) is 102°F, on July 14, 1936; the lowest is −16°F, on January 23, 1936.
The wettest calendar year on that record is 2018, with 66.71 in; the snowiest season is 1950–51, with 80.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USW00014762; records: ACIS (NOAA Regional Climate Centers), station USW00014762. Records use complete months only; a month missing more than three days is left out.
How humid and windy is West Mifflin, and how clear are its skies?
The summer (June-August) dew point averages 61°F. The muggiest month is July, with an average dew point of 62°F; the driest air comes in January (21°F). February is the windiest month (9.3 mph on average), and August has the most clear or nearly clear hours (59%).
| Month | Dew point | Humidity | Afternoon humidity | Wind | Clear or few clouds | Overcast |
|---|---|---|---|---|---|---|
| January | 21°F | 69% | 59% | 9.2 mph | 34% | 51% |
| February | 24°F | 64% | 53% | 9.3 mph | 34% | 49% |
| March | 32°F | 57% | 45% | 9.1 mph | 44% | 37% |
| April | 42°F | 58% | 44% | 8.2 mph | 47% | 29% |
| May | 54°F | 67% | 52% | 7.2 mph | 48% | 25% |
| June | 61°F | 68% | 52% | 6.8 mph | 53% | 16% |
| July | 62°F | 69% | 52% | 6.2 mph | 52% | 15% |
| August | 60°F | 70% | 52% | 6.0 mph | 59% | 16% |
| September | 50°F | 71% | 52% | 7.0 mph | 55% | 23% |
| October | 37°F | 65% | 51% | 8.0 mph | 48% | 34% |
| November | 29°F | 69% | 59% | 9.1 mph | 35% | 47% |
| December | 24°F | 72% | 64% | 9.3 mph | 33% | 52% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00014762. Monthly averages of all hours; afternoon humidity at 3 p.m. local standard time; sky as the share of hours NOAA's observations rate clear or few clouds (a dash where NOAA publishes no sky value).
How sunny is West Mifflin?
Over a year 68% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around West Mifflin, 3.7 kWh per square metre a day. August is the sunniest month (76%) and December the cloudiest (51%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 53% | 1.6 |
| February | 58% | 2.4 |
| March | 61% | 3.4 |
| April | 66% | 4.6 |
| May | 69% | 5.3 |
| June | 73% | 5.9 |
| July | 76% | 5.9 |
| August | 76% | 5.3 |
| September | 75% | 4.3 |
| October | 66% | 2.9 |
| November | 65% | 2.0 |
| December | 51% | 1.3 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does West Mifflin need?
A normal year in West Mifflin brings 5,407 heating degree days, 1% more than the median U.S. place (5,373), and 826 cooling degree days, 9% fewer than the median (908). Seven months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 3,286 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,102 | 0 |
| February | 921 | 0 |
| March | 765 | 1 |
| April | 396 | 11 |
| May | 157 | 59 |
| June | 26 | 161 |
| July | 2 | 267 |
| August | 6 | 224 |
| September | 78 | 88 |
| October | 349 | 14 |
| November | 654 | 0 |
| December | 950 | 0 |
| Year (annual) | 5,407 | 826 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00014762. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
Has West Mifflin been warmer than normal lately?
2024 averaged 56.5°F, 4.1°F above the 1991-2020 normal of 52.4°F. 4 of the 4 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 54.3°F | +1.9°F | 45.62 |
| 2022 | 53.1°F | +0.7°F | 41.30 |
| 2023 | 55.1°F | +2.7°F | 31.97 |
| 2024 | 56.5°F | +4.1°F | 36.94 |
Source: observed years: ACIS, station USW00014762. A year counts only with all twelve months complete.
How does West Mifflin's climate compare?
West Mifflin is warmer than 83 of the other 107 places with their own NOAA record in Pennsylvania, and wetter than 17. Across the 7,247 U.S. stations with normals, its annual mean of 52.4°F is warmer than 51%.
In the Köppen classification computed from these normals, West Mifflin is Dfa: continental, no dry season, hot summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near West Mifflin share this climate record?
13 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Bethel Park, PA32,376 people · 6 mi W
- Baldwin, PA20,712 people · 2 mi NW
- Whitehall, PA14,678 people · 4 mi W
- Jefferson Hills, PA12,291 people · 4 mi S
- Brentwood, PA9,704 people · 3 mi NW
- Pleasant Hills, PA8,318 people · 3 mi SW
- Castle Shannon, PA8,094 people · 5 mi W
- Dormont, PA7,922 people · 7 mi NW
- Bridgeville, PA4,620 people · 10 mi W
- Mount Oliver, PA3,259 people · 5 mi NW
- Gastonville, PA2,703 people · 8 mi SW
- Dravosburg, PA1,552 people · 2 mi E
- Finleyville, PA368 people · 8 mi SW
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about West Mifflin's climate
What is the coldest month in West Mifflin?
January, with a normal high of 37°F and a normal low of 22°F. The warmest is July (83°F by day, 64°F at night).
Does it snow in West Mifflin?
Yes. NOAA publishes no 1991-2020 snowfall normal for West Mifflin's NOAA station; the nearest record that keeps one, Murrysville (11 miles away), records 25 inches of snow in a normal year.
What is the rainiest month in West Mifflin?
June, with 4.58 in of precipitation in a normal year; the driest is February with 2.57 in.
What plant hardiness zone is West Mifflin in?
The USDA's 2023 map puts West Mifflin in zone 6b in ZIP code 15122. By the same method at West Mifflin's NOAA station, the coldest night of a typical year reaches 1°F (21 years, 1991-2020): zone 7a.
How late can frost come in West Mifflin?
In half of years the last 32°F night comes after April 18; in one year in ten it comes after May 6. Waiting until May 6 leaves about a one-in-ten chance of a later frost.
Nearby and next
- West Mifflin in OctoberThis month day by day, its records and recent years
- Pennsylvania climateThe statewide normals and every place in the state
- McKeesport, PA3 miles from this station, 51.7°F a year
- Braddock, PA4 miles from this station, 52.4°F a year
- Murrysville, PA11 miles from this station, 52.4°F a year
- Donora, PA14 miles from this station, 52.1°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made