Photo: Russ · CC BY 2.0Potomac’s winters are milder and less snowy than most of the U.S.
A typical July afternoon reaches 87°, a January night drops to 26°, and about 6 inches of snow falls in a normal winter.
A year in Potomac at a glance
Each month’s typical high and low, and what it brings.
What stands out about Potomac’s climate
Compared with towns across the U.S., with Potomac’s place in Maryland beside it.
What a year in Potomac feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 202 frost-free days a year
In half of years the last 32° night comes by April 9 and the first by October 31. Frost and day counts come from NOAA’s station at Dalecarlia Reservoir, MD, 7 miles from the town’s center, 160 ft lower.
The 2023 USDA map puts Potomac’s center in zone 7b: the coldest night of a typical winter, averaged over 1991–2020, reaches about 7°. 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 6 inches of snow a winter
Snow, measured at Dalecarlia Reservoir, MD, falls mostly in January. Precipitation (rain plus melted snow) adds up to 45 inches a year; July is the wettest month and February the driest. Rain or snow falls on about 123 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Potomac
77% of the work is heating. Months averaging under 55° run from November 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 Dalecarlia Reservoir, MD.
Living with Potomac’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
202 frost-free days in zone 7b. The last frost comes by Apr 9 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 31.
Months with highs of 62–84° and lows of 40° or more: April, May, June, September and October. 53 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Potomac from natural hazards, river flooding is the largest share (65%); heat waves, cold waves, winter storms and ice storms together are 9%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Potomac and its neighbors
Every town next door is within a degree of Potomac in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Potomac’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 |
|---|---|---|---|---|
| Potomac, MD | 26° | 87° | 45" | 5.8" |
| Ashland, KY | 24° | 87° | 45" | 6.2" |
| Ironton, OH | 24° | 87° | 44" | 6.2" |
| Bloomingdale, TN | 27° | 87° | 45" | 5.1" |
| South Boston, VA | 27° | 88° | 46" | 5.5" |
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 Potomac averaged 1.7° warmer than the 1900s. The biggest change is in December (+2.9°).
A bigger shift than in 72% 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 Potomac compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Potomac’s place among Maryland’s.
Potomac weather by month
Highs, lows and precipitation from NOAA’s grid at Potomac’s center; snow, wet days and snow on the ground from Dalecarlia Reservoir, MD. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 42° | 26° | 3.0" | 2.9" | 10 | 2 | 26° – 41° |
| February | 46° | 27° | 2.7" | 1.4" | 9 | 2 | 26° – 44° |
| March | 54° | 34° | 3.7" | 0.7" | 12 | 1 | 38° – 54° |
| April | 66° | 44° | 3.4" | 0.0" | 11 | 0 | 51° – 60° |
| May | 74° | 53° | 4.3" | 0.0" | 12 | 0 | 59° – 70° |
| June | 82° | 62° | 4.3" | 0.0" | 10 | 0 | 68° – 77° |
| July | 87° | 67° | 4.4" | 0.0" | 10 | 0 | 72° – 80° |
| August | 85° | 66° | 3.7" | 0.0" | 10 | 0 | 70° – 79° |
| September | 78° | 59° | 4.3" | 0.0" | 10 | 0 | 65° – 73° |
| October | 67° | 47° | 3.8" | 0.0" | 9 | 0 | 53° – 63° |
| November | 56° | 37° | 3.2" | 0.0" | 9 | 0 | 40° – 52° |
| December | 46° | 30° | 3.6" | 0.8" | 11 | 1 | 29° – 49° |
| Year | 65° | 46° | 44.5" | 5.8" | 123 | 6 |
How much a month can swing
A normal is an average. December swings the most: from 1991 to 2020 its average ranged from 29° to 49°. September is the most reliable, staying within 7°.
Where Potomac’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 Potomac’s center.
- Snow: Dalecarlia Reservoir, MD.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Dalecarlia Reservoir, MD, 7 miles from the town’s center, 160 ft lower; 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 Potomac’s climate
What is the weather like in Potomac?
A typical July afternoon reaches 87°, a January night drops to 26°, and about 6 inches of snow falls in a normal winter. Milder January nights than 65% of U.S. towns; hotter July afternoons than 61% of U.S. towns.
How cold does it get in Potomac in winter?
January nights average 26°. About 96 nights a year reach 32° or below. In the coldest January of the last 30 years the month averaged 26°.
How much snow does Potomac get?
About 5.8 inches in a normal winter at Dalecarlia Reservoir, MD, most of it in January, with snow on the ground about 6 days a year.
How hot does it get in Potomac?
July, with a typical high of 87° and a low of 67°. About 44 days a year reach 90° and 2 reach 100° (Dalecarlia Reservoir, MD).
When is the first and last frost in Potomac?
In half of years the last spring frost (32°) comes by April 9 and the first fall frost by October 31, about 202 frost-free days, at Dalecarlia Reservoir, MD.
What growing zone is Potomac in?
Zone 7b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 7°.
What is the best time of year to visit Potomac?
By one simple rule (highs of 62–84° and lows of 40° or more), April, May, June, September and October. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Potomac getting warmer?
Yes: 1991–2020 averaged 1.7° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 72% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Potomac.
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.