Portsmouth, Ohio climate: Normal weather by month, frost dates and records
Portsmouth's normal year runs from 23°F January nights to 87°F July afternoons, with 43.1 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 12.7°C, January lows of −5°C, July highs of 30°C, 1,094 mm of precipitation a year.
- NOAA stationPortsmouth-Sciotoville
- Station IDUSC00336781
- Location38.76°N 82.89°W
- Elevation540 ft (165 m)
- Population17,489
On October 14, the normal high in Portsmouth is 70°F and the normal low 44°F, and the chance of measurable rain or snow is 30%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Portsmouth.
- Jan 41° 23°
- Feb 45° 25°
- Mar 55° 33°
- Apr 67° 42°
- May 76° 52°
- Jun 83° 61°
- Jul 87° 65°
- Aug 86° 63°
- Sep 80° 56°
- Oct 69° 44°
- Nov 56° 33°
- Dec 46° 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 Portsmouth each month?
July is the warmest month, with normal highs of 87°F; January the coldest, with normal lows of 23°F. The most precipitation falls in May (4.60 in), the least in November (2.75 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 41°F | 23°F | 32.1°F | 3.09 | 11 | <1 | 24 | 9 h 40 min |
| February | 45°F | 25°F | 35.1°F | 3.00 | 11 | <1 | 22 | 10 h 40 min |
| March | 55°F | 33°F | 43.8°F | 4.12 | 12 | <1 | 16 | 11 h 50 min |
| April | 67°F | 42°F | 54.7°F | 3.95 | 12 | <1 | 5 | 13 h 10 min |
| May | 76°F | 52°F | 64.1°F | 4.60 | 13 | 1 | <1 | 14 h 20 min |
| June | 83°F | 61°F | 72.4°F | 4.14 | 12 | 5 | <1 | 14 h 50 min |
| July | 87°F | 65°F | 76.1°F | 4.42 | 11 | 9 | <1 | 14 h 40 min |
| August | 86°F | 63°F | 74.7°F | 3.27 | 9 | 8 | <1 | 13 h 40 min |
| September | 80°F | 56°F | 68.2°F | 3.30 | 8 | 4 | <1 | 12 h 30 min |
| October | 69°F | 44°F | 56.3°F | 2.95 | 9 | <1 | 3 | 11 h 20 min |
| November | 56°F | 33°F | 44.8°F | 2.75 | 10 | <1 | 15 | 10 h 10 min |
| December | 46°F | 28°F | 36.7°F | 3.50 | 12 | <1 | 22 | 9 h 30 min |
| Year (annual) | 66°F | 44°F | 54.9°F | 43.09 | 131 | 26 | 106 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 5°C | −5°C | 0.1°C | 78 mm |
| February | 7°C | −4°C | 1.7°C | 76 mm |
| March | 13°C | 0°C | 6.6°C | 105 mm |
| April | 20°C | 6°C | 12.6°C | 100 mm |
| May | 24°C | 11°C | 17.8°C | 117 mm |
| June | 29°C | 16°C | 22.4°C | 105 mm |
| July | 30°C | 19°C | 24.5°C | 112 mm |
| August | 30°C | 17°C | 23.7°C | 83 mm |
| September | 27°C | 13°C | 20.1°C | 84 mm |
| October | 21°C | 6°C | 13.5°C | 75 mm |
| November | 13°C | 1°C | 7.1°C | 70 mm |
| December | 8°C | −2°C | 2.6°C | 89 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Warnock 2 (19 miles away), gets 21 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00336781; 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 Portsmouth?
Normal highs sit between 65°F and 85°F in April, May, June, September and October. Of those, September has the fewest days with rain (8).
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 USC00336781.
When is the last frost in Portsmouth?
In Portsmouth, the last spring frost (32°F) comes after April 17 in half of years and after May 5 in one year in ten; the first autumn frost comes before October 25 in half of years and before October 11 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 171 year in 10 after May 5; 9 in 10 after April 3
- First autumn frost, half of years before
- October 251 year in 10 before October 11; 9 in 10 before November 6
NOAA puts the median frost-free season at 191 days, and the season without a hard freeze (28°F) at 214 days.
A hard freeze (28°F) comes after April 4 in half of springs and before November 4 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Portsmouth in zone 7a in ZIP code 45662. By the map's own method, the average of each year's coldest night over 1991-2020, Portsmouth's NOAA station is in zone 7a: the coldest night of a typical year reaches 2°F (22 complete years).
Frost dates for every NOAA station in Ohio · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00336781; 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 Portsmouth?
In a normal year in Portsmouth, 26 days a year reach 90°F, 106 nights fall to 32°F or colder and 131 days bring measurable precipitation.
- Days at 90°F or more
- 26a 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
- 16high of 32°F or less
- Days with 0.01 inch of precipitation
- 131a normal year
The highest temperature in this station's record (since 1893) is 107°F, on July 28, 1930; the lowest is −29°F, on January 19, 1994.
The wettest calendar year on that record is 2018, with 59.92 in; the snowiest season is 1959–60, with 40.2 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00336781; records: ACIS (NOAA Regional Climate Centers), station USC00336781. Records use complete months only; a month missing more than three days is left out.
How sunny is Portsmouth?
Over a year 72% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Portsmouth, 4.0 kWh per square metre a day. August is the sunniest month (80%) and December the cloudiest (59%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 60% | 1.9 |
| February | 60% | 2.6 |
| March | 65% | 3.7 |
| April | 71% | 5.0 |
| May | 72% | 5.5 |
| June | 78% | 6.2 |
| July | 77% | 5.9 |
| August | 80% | 5.5 |
| September | 78% | 4.5 |
| October | 72% | 3.3 |
| November | 70% | 2.3 |
| December | 59% | 1.6 |
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 Portsmouth need?
A normal year in Portsmouth brings 4,788 heating degree days, 11% fewer than the median U.S. place (5,373), and 1,142 cooling degree days, 26% more than the median (908). Six months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 3,784 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,020 | 0 |
| February | 837 | 0 |
| March | 659 | 1 |
| April | 322 | 13 |
| May | 114 | 86 |
| June | 11 | 232 |
| July | 0 | 343 |
| August | 2 | 302 |
| September | 47 | 143 |
| October | 292 | 20 |
| November | 605 | 0 |
| December | 879 | 0 |
| Year (annual) | 4,788 | 1,142 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00336781. 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 Portsmouth been warmer than normal lately?
2025 averaged 54.8°F, 0.1°F below the 1991-2020 normal of 54.9°F. 3 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 55.2°F | +0.3°F | 48.91 |
| 2022 | 54.2°F | −0.7°F | 41.83 |
| 2023 | 55.9°F | +1.0°F | 40.86 |
| 2024 | 57.0°F | +2.1°F | 48.31 |
| 2025 | 54.8°F | −0.1°F | 46.38 |
Over 122 complete years from 1859 to 2025, the station's annual mean temperature rose at a fitted 0.6°F per century (+0.04°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00336781; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Portsmouth's climate compare?
Portsmouth is warmer than 96 of the other 98 places with their own NOAA record in Ohio, and wetter than 67. Across the 7,247 U.S. stations with normals, its annual mean of 54.9°F is warmer than 60%.
In the Köppen classification computed from these normals, Portsmouth is Cfa: temperate, 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 Portsmouth share this climate record?
11 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.
- Wheelersburg, OH6,414 people · 2 mi SE
- West Portsmouth, OH2,806 people · 8 mi W
- New Boston, OH2,227 people · 3 mi W
- Rosemount, OH1,995 people · 5 mi W
- Vanceburg, KY1,385 people · 26 mi SW
- Greenup, KY1,079 people · 14 mi S
- South Shore, KY1,042 people · 5 mi SW
- Sciotodale, OH836 people · 2 mi E
- Garrison, KY748 people · 19 mi SW
- South Webster, OH651 people · 9 mi NE
- Minford, OH487 people · 8 mi N
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 Portsmouth's climate
What is the coldest month in Portsmouth?
January, with a normal high of 41°F and a normal low of 23°F. The warmest is July (87°F by day, 65°F at night).
Does it snow in Portsmouth?
Yes. NOAA publishes no 1991-2020 snowfall normal for Portsmouth's NOAA station; the nearest record that keeps one, Warnock 2 (19 miles away), records 21 inches of snow in a normal year.
What is the rainiest month in Portsmouth?
May, with 4.60 in of precipitation in a normal year; the driest is November with 2.75 in.
What plant hardiness zone is Portsmouth in?
The USDA's 2023 map puts Portsmouth in zone 7a in ZIP code 45662. By the same method at Portsmouth's NOAA station, the coldest night of a typical year reaches 2°F (22 years, 1991-2020): zone 7a.
How late can frost come in Portsmouth?
In half of years the last 32°F night comes after April 17; in one year in ten it comes after May 5. Waiting until May 5 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Ohio climateThe statewide normals and every place in the state
- Lucasville, OH11 miles from this station, 54.0°F a year
- Warnock 2, KY19 miles from this station, 54.5°F a year
- Waterloo, OH22 miles from this station, 52.8°F a year
- Jackson, OH24 miles from this station, 51.5°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made