Packhorse Ford · Photo: Acroterion · CC BY-SA 4.0In Antietam, July heat, January chill and rainfall all sit near the middle of U.S. towns
On a normal July day the thermometer tops out near 87°. Summer afternoons here are warmer than in 63% of U.S. towns. Compared with 1901–2000, the average now sits 1.5° higher. The frost-free window for a garden runs roughly April 26 to October 18.
A year in Antietam at a glance
Each month’s typical high and low, and what it brings.
What stands out about Antietam’s climate
Compared with towns across the U.S., with Antietam’s place in Maryland beside it.
What a year in Antietam feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 175 frost-free days a year
In half of years the last 32° night comes by April 26 and the first by October 18. Frost and day counts come from NOAA’s station at Sharpsburg 5 S, MD, 1.4 miles from the town’s center, at about the same height.
The 2023 USDA map puts Antietam’s center in zone 7a: the coldest night of a typical winter, averaged over 1991–2020, reaches about 1°. 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 41 inches of rain a year
May is the wettest month and February the driest.
Rain + melted snow by month
Inches of water
Heating and cooling a home in Antietam
86% of the work is heating, so the furnace matters far more than the air conditioner. 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 Sharpsburg 5 S, MD.
Living with Antietam’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
175 frost-free days in zone 7a. The last frost comes by Apr 26 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 18.
Months with highs of 62–84° and lows of 40° or more: April, May, June, September and October. 0.0 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Antietam from natural hazards, river flooding is the largest share (51%); heat waves, cold waves, winter storms and ice storms together are 8%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Antietam and similar climates
TownRatings has no climate map of the towns around Antietam yet.
Temperatures and precipitation come from NOAA’s 5 km grid; snow and day counts from the stations named on this page.
Warmer than it used to be
The last 30 years in Antietam averaged 1.5° warmer than the 1900s. The biggest change is in December (+2.8°).
A bigger shift than in 58% 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 Antietam compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Antietam’s place among Maryland’s.
Antietam weather by month
Highs, lows and precipitation from NOAA’s grid at Antietam’s center. 1991–2020 normals.
| Month | High | Low | Rain + melt | 30-yr range |
|---|---|---|---|---|
| January | 41° | 24° | 2.8" | 24° – 40° |
| February | 45° | 26° | 2.4" | 25° – 43° |
| March | 53° | 32° | 3.5" | 37° – 52° |
| April | 66° | 42° | 3.4" | 50° – 59° |
| May | 75° | 51° | 4.3" | 58° – 69° |
| June | 83° | 60° | 3.7" | 67° – 74° |
| July | 87° | 64° | 4.0" | 71° – 79° |
| August | 85° | 63° | 3.2" | 69° – 77° |
| September | 78° | 55° | 4.3" | 64° – 71° |
| October | 67° | 44° | 3.2" | 52° – 63° |
| November | 55° | 34° | 3.0" | 39° – 50° |
| December | 45° | 28° | 3.3" | 27° – 46° |
| Year | 65° | 43° | 41.1" |
How much a month can swing
A normal is an average. December swings the most: from 1991 to 2020 its average ranged from 27° to 46°. September is the most reliable, staying within 7°.
Where Antietam’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 Antietam’s center.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Sharpsburg 5 S, MD, 1.4 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 Antietam’s climate
What is the weather like in Antietam?
A typical July afternoon reaches 87°, a January night drops to 24°. Milder January nights than 59% of U.S. towns; hotter July afternoons than 63% of U.S. towns.
How cold does it get in Antietam in winter?
January nights average 24°. About 126 nights a year reach 32° or below and 2 reach 0° or below. In the coldest January of the last 30 years the month averaged 24°.
How hot does it get in Antietam?
July, with a typical high of 87° and a low of 64°. About 25 days a year reach 90° (Sharpsburg 5 S, MD).
When is the first and last frost in Antietam?
In half of years the last spring frost (32°) comes by April 26 and the first fall frost by October 18, about 175 frost-free days, at Sharpsburg 5 S, MD.
What growing zone is Antietam in?
Zone 7a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 1°.
What is the best time of year to visit Antietam?
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 Antietam getting warmer?
Yes: 1991–2020 averaged 1.5° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 58% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Antietam.
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.