National Arboretum DC, Maryland climate: Climate normals at a NOAA weather station
National Arboretum DC's normal year runs from 28°F January nights to 90°F July afternoons, with 45.6 inches of precipitation and 10 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 14.6°C, January lows of −2°C, July highs of 32°C, 1,158 mm of precipitation a year.
- NOAA stationNational Arboretum DC
- Station IDUSC00186350
- Location38.91°N 76.97°W
- Elevation50 ft (15 m)
On October 23, the normal high in National Arboretum DC is 67°F and the normal low 46°F, and the chance of measurable rain or snow is 31%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for National Arboretum DC.
- Jan 45° 28°
- Feb 48° 30°
- Mar 56° 37°
- Apr 68° 46°
- May 77° 57°
- Jun 85° 66°
- Jul 90° 71°
- Aug 88° 69°
- Sep 82° 62°
- Oct 70° 49°
- Nov 58° 39°
- Dec 49° 32°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like at National Arboretum DC each month?
July is the warmest month, with normal highs of 90°F; January the coldest, with normal lows of 28°F. The most precipitation falls in July (4.62 in), the least in February (2.77 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 45°F | 28°F | 36.2°F | 3.03 | 4.7 | 10 | <1 | 23 | 9 h 40 min |
| February | 48°F | 30°F | 38.6°F | 2.77 | 2.3 | 9 | <1 | 20 | 10 h 40 min |
| March | 56°F | 37°F | 46.2°F | 3.96 | 1.4 | 10 | <1 | 12 | 11 h 50 min |
| April | 68°F | 46°F | 57.0°F | 3.44 | 0.0 | 12 | 1 | 1 | 13 h 10 min |
| May | 77°F | 57°F | 66.7°F | 4.32 | 0.0 | 12 | 3 | <1 | 14 h 20 min |
| June | 85°F | 66°F | 75.7°F | 4.56 | 0.0 | 11 | 9 | <1 | 14 h 50 min |
| July | 90°F | 71°F | 80.3°F | 4.62 | 0.0 | 11 | 17 | <1 | 14 h 40 min |
| August | 88°F | 69°F | 78.6°F | 3.67 | 0.0 | 10 | 13 | <1 | 13 h 40 min |
| September | 82°F | 62°F | 71.6°F | 4.12 | 0.0 | 10 | 4 | <1 | 12 h 30 min |
| October | 70°F | 49°F | 59.4°F | 4.23 | 0.0 | 9 | <1 | 1 | 11 h 20 min |
| November | 58°F | 39°F | 48.6°F | 3.20 | 0.0 | 8 | <1 | 8 | 10 h 10 min |
| December | 49°F | 32°F | 40.6°F | 3.67 | 1.3 | 9 | <1 | 19 | 9 h 30 min |
| Year (annual) | 68°F | 49°F | 58.3°F | 45.59 | 9.7 | 121 | 48 | 84 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 7°C | −2°C | 2.3°C | 77 mm | 12 cm |
| February | 9°C | −1°C | 3.7°C | 70 mm | 6 cm |
| March | 13°C | 3°C | 7.9°C | 101 mm | 4 cm |
| April | 20°C | 8°C | 13.9°C | 87 mm | 0 cm |
| May | 25°C | 14°C | 19.3°C | 110 mm | 0 cm |
| June | 30°C | 19°C | 24.3°C | 116 mm | 0 cm |
| July | 32°C | 22°C | 26.8°C | 117 mm | 0 cm |
| August | 31°C | 20°C | 25.9°C | 93 mm | 0 cm |
| September | 28°C | 16°C | 22.0°C | 105 mm | 0 cm |
| October | 21°C | 9°C | 15.2°C | 107 mm | 0 cm |
| November | 15°C | 4°C | 9.2°C | 81 mm | 0 cm |
| December | 10°C | 0°C | 4.8°C | 93 mm | 3 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00186350; 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.
Which months are mildest at National Arboretum DC?
Normal highs sit between 65°F and 85°F in April, May, September and October. Of those, October has the fewest days with rain (9).
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 USC00186350.
When is the last frost at National Arboretum DC?
In National Arboretum DC, the last spring frost (32°F) comes after March 29 in half of years and after April 11 in one year in ten; the first autumn frost comes before November 8 in half of years and before October 26 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
- March 291 year in 10 after April 11; 9 in 10 after March 15
- First autumn frost, half of years before
- November 81 year in 10 before October 26; 9 in 10 before November 23
NOAA puts the median frost-free season at 224 days, and the season without a hard freeze (28°F) at 248 days.
A hard freeze (28°F) comes after March 17 in half of springs and before November 20 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts National Arboretum DC in zone 7b in ZIP code 20018, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, the station is in zone 8a: the coldest night of a typical year reaches 11°F (19 complete years); the map interpolates between stations and terrain, so the station and the ZIP area can differ by half a zone.
Frost dates for every NOAA station in Maryland · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00186350; 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 at National Arboretum DC?
In a normal year in National Arboretum DC, 48 days a year reach 90°F (2 of them 100°F or more), 84 nights fall to 32°F or colder and 121 days bring measurable precipitation.
- Days at 90°F or more
- 48a normal year
- Days at 100°F or more
- 2a normal year
- Nights at 32°F or colder
- 84a normal year
- Days that stay below freezing
- 8high of 32°F or less
- Days with 0.01 inch of precipitation
- 121a normal year
- Days with 1 inch of snow or more
- 3a normal year
The highest temperature in this station's record (since 1948) is 106°F, on July 30, 2011; the lowest is −10°F, on January 17, 1982.
The wettest calendar year on that record is 2003, with 71.52 in; the snowiest season is 1960–61, with 54.9 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00186350; records: ACIS (NOAA Regional Climate Centers), station USC00186350. Records use complete months only; a month missing more than three days is left out.
How sunny is it at National Arboretum DC?
Over a year 77% of the sunlight that would reach the ground under clear skies gets through the clouds at National Arboretum DC, 4.2 kWh per square metre a day. July is the sunniest month (84%) and January the cloudiest (71%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 71% | 2.2 |
| February | 72% | 3.0 |
| March | 72% | 4.0 |
| April | 75% | 5.2 |
| May | 76% | 5.8 |
| June | 82% | 6.4 |
| July | 84% | 6.3 |
| August | 82% | 5.6 |
| September | 79% | 4.5 |
| October | 76% | 3.4 |
| November | 76% | 2.5 |
| December | 71% | 1.9 |
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 many heating and cooling degree days does National Arboretum DC record?
A normal year at National Arboretum DC brings 4,049 heating degree days, 25% fewer than the median U.S. place (5,373), and 1,649 cooling degree days, 82% more than the median (908). Five months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 4,518 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 891 | 0 |
| February | 738 | 0 |
| March | 586 | 3 |
| April | 269 | 29 |
| May | 75 | 129 |
| June | 7 | 329 |
| July | 0 | 476 |
| August | 0 | 422 |
| September | 21 | 219 |
| October | 210 | 38 |
| November | 492 | 2 |
| December | 759 | 1 |
| Year (annual) | 4,049 | 1,649 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00186350. 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.
Have recent years at National Arboretum DC been warmer than normal?
Over 48 complete years from 1949 to 2019, the station's annual mean temperature rose at a fitted 4.1°F per century (+0.23°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does National Arboretum DC's climate compare?
National Arboretum DC is warmer than 23 of the 26 places with their own NOAA record in Maryland, and wetter than 11. Across the 7,247 U.S. stations with normals, its annual mean of 58.3°F is warmer than 70%.
In the Köppen classification computed from these normals, National Arboretum DC 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.
Questions about National Arboretum DC's climate
What is the coldest month at National Arboretum DC?
January, with a normal high of 45°F and a normal low of 28°F. The warmest is July (90°F by day, 71°F at night).
Does it snow at National Arboretum DC?
Yes: 10 inches in a normal year, falling on 7 days with 0.1 inch or more, the most in January (4.7 inches).
What is the rainiest month at National Arboretum DC?
July, with 4.62 in of precipitation in a normal year; the driest is February with 2.77 in.
What plant hardiness zone is National Arboretum DC in?
The USDA's 2023 map puts National Arboretum DC in zone 7b in ZIP code 20018, the nearest ZIP area. By the same method at the station, the coldest night of a typical year reaches 11°F (19 years, 1991-2020): zone 8a.
How late can frost come at National Arboretum DC?
In half of years the last 32°F night comes after March 29; in one year in ten it comes after April 11. Waiting until April 11 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Maryland climateThe statewide normals and every place in the state
- Washington, DC6 miles from this station, 59.3°F a year
- Dalecarlia Reservoir, MD8 miles from this station, 56.2°F a year
- Oxon Hill, MD8 miles from this station, 57.1°F a year
- Beltsville, MD8 miles from this station, 55.9°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made