Mercer, Pennsylvania climate: Normal weather by month, frost dates and records
Mercer's normal year runs from 16°F January nights to 82°F July afternoons. (NOAA 1991-2020 normals)
In metric: a yearly mean of 9.2°C, January lows of −9°C, July highs of 28°C.
- NOAA stationMercer
- Station IDUSC00365651
- Location41.22°N 80.23°W
- Elevation1,220 ft (372 m)
- From the centerunder 1 mile
- Population1,922
On October 23, the normal high in Mercer is 61°F and the normal low 36°F.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Mercer.
- Jan 35° 16°
- Feb 39° 17°
- Mar 48° 25°
- Apr 62° 34°
- May 71° 44°
- Jun 79° 53°
- Jul 82° 56°
- Aug 82° 56°
- Sep 75° 49°
- Oct 63° 38°
- Nov 50° 29°
- Dec 40° 21°
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 Mercer each month?
July is the warmest month, with normal highs of 82°F; January the coldest, with normal lows of 16°F.
| Month | High | Low | Mean | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|
| January | 35°F | 16°F | 25.5°F | – | <1 | 28 | 9 h 30 min |
| February | 39°F | 17°F | 27.9°F | – | <1 | 26 | 10 h 40 min |
| March | 48°F | 25°F | 36.5°F | – | <1 | 25 | 11 h 50 min |
| April | 62°F | 34°F | 47.8°F | – | <1 | 14 | 13 h 20 min |
| May | 71°F | 44°F | 57.6°F | – | <1 | 4 | 14 h 30 min |
| June | 79°F | 53°F | 65.9°F | – | 1 | <1 | 15 h 10 min |
| July | 82°F | 56°F | 69.2°F | – | 2 | <1 | 14 h 50 min |
| August | 82°F | 56°F | 68.7°F | – | 2 | <1 | 13 h 50 min |
| September | 75°F | 49°F | 61.9°F | – | <1 | 1 | 12 h 30 min |
| October | 63°F | 38°F | 50.7°F | – | <1 | 12 | 11 h 10 min |
| November | 50°F | 29°F | 39.7°F | – | <1 | 21 | 9 h 50 min |
| December | 40°F | 21°F | 30.6°F | – | <1 | 28 | 9 h 10 min |
| Year (annual) | 60°F | 37°F | 48.5°F | – | 6 | 159 |
The same normals in °C and millimetres
| Month | High | Low | Mean |
|---|---|---|---|
| January | 2°C | −9°C | −3.6°C |
| February | 4°C | −8°C | −2.3°C |
| March | 9°C | −4°C | 2.5°C |
| April | 17°C | 1°C | 8.8°C |
| May | 22°C | 7°C | 14.2°C |
| June | 26°C | 12°C | 18.8°C |
| July | 28°C | 14°C | 20.7°C |
| August | 28°C | 13°C | 20.4°C |
| September | 24°C | 9°C | 16.6°C |
| October | 17°C | 3°C | 10.4°C |
| November | 10°C | −2°C | 4.3°C |
| December | 4°C | −6°C | −0.8°C |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, New Castle (16 miles away), gets 28 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00365651; 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 Mercer?
Normal highs sit between 65°F and 85°F in May, June, July, August and September.
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 USC00365651.
When is the last frost in Mercer?
In Mercer, the last spring frost (32°F) comes after May 15 in half of years and after June 1 in one year in ten; the first autumn frost comes before October 3 in half of years and before September 19 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
- May 151 year in 10 after June 1; 9 in 10 after April 30
- First autumn frost, half of years before
- October 31 year in 10 before September 19; 9 in 10 before October 19
NOAA puts the median frost-free season at 140 days, and the season without a hard freeze (28°F) at 163 days.
A hard freeze (28°F) comes after May 3 in half of springs and before October 13 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Mercer in zone 6a in ZIP code 16137, the nearest ZIP area.
Frost dates for every NOAA station in Pennsylvania · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00365651; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. 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 Mercer?
In a normal year in Mercer, 6 days a year reach 90°F and 159 nights fall to 32°F or colder.
- Days at 90°F or more
- 6a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 159a normal year
- Days that stay below freezing
- 32high of 32°F or less
The highest temperature in this station's record (since 1950) is 101°F, on September 2, 1953; the lowest is −32°F, on January 19, 1994.
The wettest calendar year on that record is 1977, with 46.68 in; the snowiest season is 1984–85, with 82.3 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00365651; records: ACIS (NOAA Regional Climate Centers), station USC00365651. Records use complete months only; a month missing more than three days is left out.
How sunny is Mercer?
Over a year 68% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Mercer, 3.6 kWh per square metre a day. July is the sunniest month (77%) and December the cloudiest (47%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 51% | 1.4 |
| February | 57% | 2.3 |
| March | 60% | 3.3 |
| April | 65% | 4.5 |
| May | 69% | 5.3 |
| June | 74% | 5.9 |
| July | 77% | 5.9 |
| August | 77% | 5.2 |
| September | 74% | 4.2 |
| October | 64% | 2.7 |
| November | 61% | 1.8 |
| December | 47% | 1.1 |
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 Mercer need?
A normal year in Mercer brings 6,444 heating degree days, 20% more than the median U.S. place (5,373), and 465 cooling degree days, 49% 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 2,525 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,224 | 0 |
| February | 1,039 | 0 |
| March | 882 | 0 |
| April | 519 | 3 |
| May | 258 | 27 |
| June | 67 | 95 |
| July | 23 | 151 |
| August | 25 | 139 |
| September | 139 | 46 |
| October | 446 | 5 |
| November | 757 | 0 |
| December | 1,066 | 0 |
| Year (annual) | 6,444 | 465 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00365651. 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.
How does Mercer's climate compare?
Mercer is warmer than 33 of the other 107 places with their own NOAA record in Pennsylvania. Across the 7,247 U.S. stations with normals, its annual mean of 48.5°F is warmer than 34%.
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers.
Which places near Mercer share this climate record?
8 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.
- West Hill, OH2,345 people · 15 mi W
- Masury, OH2,292 people · 16 mi W
- Stoneboro, PA923 people · 10 mi NE
- Lake Latonka, PA741 people · 5 mi NE
- Sandy Lake, PA630 people · 12 mi NE
- Fredonia, PA421 people · 7 mi N
- Jackson Center, PA186 people · 6 mi NE
- Volant, PA122 people · 8 mi S
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 Mercer's climate
What is the coldest month in Mercer?
January, with a normal high of 35°F and a normal low of 16°F. The warmest is July (82°F by day, 56°F at night).
Does it snow in Mercer?
Yes. NOAA publishes no 1991-2020 snowfall normal for Mercer's NOAA station; the nearest record that keeps one, New Castle (16 miles away), records 28 inches of snow in a normal year.
What plant hardiness zone is Mercer in?
The USDA's 2023 map puts Mercer in zone 6a in ZIP code 16137, the nearest ZIP area.
How late can frost come in Mercer?
In half of years the last 32°F night comes after May 15; in one year in ten it comes after June 1. Waiting until June 1 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Pennsylvania climateThe statewide normals and every place in the state
- Slippery Rock, PA15 miles from this station, 48.1°F a year
- New Castle, PA16 miles from this station, 51.1°F a year
- Jamestown, PA22 miles from this station, 48.3°F a year
- Youngstown, OH23 miles from this station, 49.9°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made