Christiana Lindsey House · Photo: Nyttend · Public domainMercer’s winters are colder and snowier than most of the U.S.
A typical July afternoon reaches 83°, a January night drops to 18°, and about 28 inches of snow falls in a normal winter.
A year in Mercer at a glance
Each month’s typical high and low, and what it brings.
What stands out about Mercer’s climate
Compared with towns across the U.S., with Mercer’s place in Pennsylvania beside it.
What a year in Mercer feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 140 frost-free days a year
In half of years the last 32° night comes by May 15 and the first by October 3. Frost and day counts come from NOAA’s station at Mercer, PA, 0.1 miles from the town’s center, at about the same height.
The 2023 USDA map puts Mercer’s center in zone 6a: the coldest night of a typical winter, averaged over 1991–2020, reaches about −8°. 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 28 inches of snow a winter
Snow, measured at New Castle 1 N, PA, falls mostly in January. Precipitation (rain plus melted snow) adds up to 44 inches a year; July is the wettest month and February the driest. Rain or snow falls on about 156 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Mercer
93% 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 Mercer, PA.
Living with Mercer’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
140 frost-free days in zone 6a. The last frost comes by May 15 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 3.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August, September and October. 0.1 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Mercer from natural hazards, river flooding is the largest share (84%); heat waves, cold waves, winter storms and ice storms together are 2%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Mercer and its neighbors
Every town next door is within a degree of Mercer in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Mercer’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 |
|---|---|---|---|---|
| Mercer, PA | 18° | 83° | 44" | 28" |
| Bellefontaine, OH | 19° | 83° | 42" | 26" |
| Frankfort, IN | 18° | 84° | 43" | 24" |
| Montville, CT | 20° | 83° | 47" | 28" |
| Ghent, NY | 16° | 84° | 42" | 31" |
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 Mercer averaged 1.7° warmer than the 1900s. The biggest change is in December (+2.8°).
A bigger shift than in 71% 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 Mercer compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Mercer’s place among Pennsylvania’s.
Mercer weather by month
Highs, lows and precipitation from NOAA’s grid at Mercer’s center; snow, wet days and snow on the ground from New Castle 1 N, PA. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 34° | 18° | 3.1" | 10.1" | 16 | 16 | 18° – 36° |
| February | 38° | 20° | 2.4" | 7.7" | 12 | 12 | 14° – 37° |
| March | 47° | 27° | 3.2" | 3.7" | 12 | 5 | 30° – 49° |
| April | 61° | 36° | 4.0" | 0.3" | 15 | 0 | 42° – 54° |
| May | 71° | 46° | 4.1" | 0.0" | 14 | 0 | 51° – 65° |
| June | 79° | 55° | 4.6" | 0.0" | 13 | 0 | 62° – 70° |
| July | 83° | 59° | 4.7" | 0.0" | 12 | 0 | 66° – 75° |
| August | 81° | 58° | 3.9" | 0.0" | 11 | 0 | 65° – 74° |
| September | 75° | 51° | 4.0" | 0.0" | 11 | 0 | 59° – 68° |
| October | 63° | 41° | 3.5" | 0.0" | 12 | 0 | 48° – 58° |
| November | 50° | 32° | 3.2" | 0.8" | 13 | 2 | 35° – 47° |
| December | 39° | 24° | 3.3" | 4.9" | 14 | 7 | 22° – 43° |
| Year | 60° | 39° | 44.0" | 27.5" | 156 | 42 |
How much a month can swing
A normal is an average. February swings the most: from 1991 to 2020 its average ranged from 14° to 37°. June is the most reliable, staying within 8°.
Where Mercer’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 Mercer’s center.
- Snow: New Castle 1 N, PA.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Mercer, PA, 0.1 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 Mercer’s climate
What is the weather like in Mercer?
A typical July afternoon reaches 83°, a January night drops to 18°, and about 28 inches of snow falls in a normal winter. Colder January nights than 69% of U.S. towns; cooler July afternoons than 76% of U.S. towns.
How cold does it get in Mercer in winter?
January nights average 18°. About 159 nights a year reach 32° or below and 9 reach 0° or below. In the coldest January of the last 30 years the month averaged 18°.
How much snow does Mercer get?
About 28 inches in a normal winter at New Castle 1 N, PA, most of it in January, with snow on the ground about 42 days a year.
How hot does it get in Mercer?
July, with a typical high of 83° and a low of 59°. About 6 days a year reach 90° (Mercer, PA).
When is the first and last frost in Mercer?
In half of years the last spring frost (32°) comes by May 15 and the first fall frost by October 3, about 140 frost-free days, at Mercer, PA.
What growing zone is Mercer in?
Zone 6a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −8°.
What is the best time of year to visit Mercer?
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 Mercer getting warmer?
Yes: 1991–2020 averaged 1.7° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 71% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Mercer.
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.