National Harbor, MD climate
National Harbor has chilly winters and warm summers. A typical July afternoon reaches 89°, a January night drops to 27°, and about 13 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in National Harbor feels like
Winter
Spring
Summer
Fall
National Harbor weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 45° | 27° | 3.0" | 4.8" | 10 | 4 | 28° – 42° |
| February | 48° | 29° | 2.6" | 3.5" | 9 | 5 | 28° – 46° |
| March | 56° | 35° | 3.8" | 2.8" | 9 | 2 | 40° – 55° |
| April | 68° | 45° | 3.4" | 0 | 11 | 0 | 53° – 62° |
| May | 76° | 55° | 4.0" | 0 | 12 | 0 | 61° – 71° |
| June | 85° | 64° | 4.2" | 0 | 11 | 0 | 70° – 79° |
| July | 89° | 69° | 4.6" | 0 | 9 | 0 | 74° – 82° |
| August | 87° | 67° | 3.8" | 0 | 10 | 0 | 72° – 81° |
| September | 80° | 60° | 4.3" | 0 | 8 | 0 | 67° – 74° |
| October | 69° | 48° | 3.8" | 0 | 9 | 0 | 54° – 65° |
| November | 58° | 38° | 3.0" | 0.1" | 8 | 0 | 42° – 53° |
| December | 48° | 31° | 3.6" | 2.2" | 10 | 1 | 31° – 51° |
| Year | 67° | 47° | 44.1" | 13.4" | 116 | 12 |
“Wet days” have at least 0.01" of rain or melted snow. “Snow on ground” counts days with 1" or more. The 30-year range is the coldest and warmest that month’s average temperature got between 1991 and 2020.
Rain and snow in National Harbor
National Harbor gets 44 inches of rain and melted snow a year. July is the wettest month and February the driest. Rain or snow falls on about 116 days a year. Snow covers the ground about 12 days of the year.
About 217 frost-free days a year
In half of years the last 32° night comes by April 3 and the first one by November 8. That leaves about 217 frost-free days for gardens, longer than 81% of U.S. towns.
Heating and cooling a home in National Harbor
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In National Harbor, 75% of that work is heating and 25% is cooling.
Degree days measure how far each day’s average temperature falls below or rises above 65°, added up over a year. Source: NOAA station normals.
National Harbor and its neighbors
National Harbor borders 3 towns with climate data. January nights across them vary by 0.4°. Oxon Hill has the coldest January nights (27°) and Forest Heights the hottest July afternoons (89°). National Harbor’s January low is 27° and its July high 89°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How National Harbor compares
Compared with every U.S. town and city on TownTapestry, each counted once.
Warmer than it used to be
The last 30 years in National Harbor averaged 1.7° warmer than the 1900s. The biggest change is in December (+2.8°). The shift is larger than in 80% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at National Harbor’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. December swings the most: between 1991 and 2020 its average temperature ranged from 31° to 51°. September is the most reliable, staying within 8°.
Common questions about National Harbor’s climate
What is the coldest month in National Harbor?
January, with a typical high of 45° and a low of 27°.
What is the hottest month in National Harbor?
July, with a typical high of 89° and a low of 69°. About 38 days a year reach 90°.
How much snow does National Harbor get?
About 13 inches in a normal winter, most of it in January.
When is the first frost in National Harbor?
In half of years the first 32° night comes by November 8, and the last spring frost by April 3.
What is the rainiest month in National Harbor?
July, with 4.6 inches of rain and melted snow. The year totals 44 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for National Harbor itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Franconia 1.3 Sse, VA (7 mi, snow) and Oxon Hill, MD (1 mi, frost, heat and degree days). Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.