Duncan, Oklahoma climate: Normal weather by month, frost dates and records
Duncan's normal year runs from 28°F January nights to 94°F July afternoons, with 37.1 inches of precipitation and 3 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 16.6°C, January lows of −2°C, July highs of 34°C, 943 mm of precipitation a year.
- NOAA stationDuncan
- Station IDUSC00342660
- Location34.50°N 97.96°W
- Elevation1,125 ft (343 m)
- Population23,174
On October 23, the normal high in Duncan is 73°F and the normal low 48°F, and the chance of measurable rain or snow is 22%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Duncan.
- Jan 52° 28°
- Feb 57° 32°
- Mar 65° 41°
- Apr 73° 49°
- May 81° 59°
- Jun 89° 68°
- Jul 94° 72°
- Aug 93° 71°
- Sep 86° 63°
- Oct 76° 51°
- Nov 64° 39°
- Dec 54° 31°
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 Duncan each month?
July is the warmest month, with normal highs of 94°F; January the coldest, with normal lows of 28°F. The most precipitation falls in May (5.58 in), the least in January (1.52 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 52°F | 28°F | 40.2°F | 1.52 | 1.1 | 5 | <1 | 22 | 10 h |
| February | 57°F | 32°F | 44.2°F | 1.84 | 0.4 | 6 | <1 | 15 | 11 h |
| March | 65°F | 41°F | 53.0°F | 2.76 | 0.2 | 7 | <1 | 6 | 11 h 50 min |
| April | 73°F | 49°F | 61.2°F | 3.45 | 0.0 | 7 | 1 | 1 | 13 h |
| May | 81°F | 59°F | 69.7°F | 5.58 | 0.0 | 9 | 4 | <1 | 14 h |
| June | 89°F | 68°F | 78.2°F | 4.49 | 0.0 | 8 | 14 | <1 | 14 h 30 min |
| July | 94°F | 72°F | 82.6°F | 2.58 | 0.0 | 6 | 24 | <1 | 14 h 20 min |
| August | 93°F | 71°F | 82.0°F | 2.90 | 0.0 | 6 | 24 | <1 | 13 h 30 min |
| September | 86°F | 63°F | 74.6°F | 3.79 | 0.0 | 7 | 9 | <1 | 12 h 30 min |
| October | 76°F | 51°F | 63.1°F | 3.86 | 0.0 | 7 | 1 | <1 | 11 h 20 min |
| November | 64°F | 39°F | 51.3°F | 2.33 | 0.3 | 6 | <1 | 7 | 10 h 20 min |
| December | 54°F | 31°F | 42.1°F | 2.04 | 0.8 | 6 | <1 | 19 | 9 h 50 min |
| Year (annual) | 73°F | 50°F | 61.9°F | 37.14 | 2.8 | 81 | 76 | 69 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 11°C | −2°C | 4.6°C | 39 mm | 3 cm |
| February | 14°C | 0°C | 6.8°C | 47 mm | 1 cm |
| March | 18°C | 5°C | 11.7°C | 70 mm | 1 cm |
| April | 23°C | 9°C | 16.2°C | 88 mm | 0 cm |
| May | 27°C | 15°C | 20.9°C | 142 mm | 0 cm |
| June | 31°C | 20°C | 25.7°C | 114 mm | 0 cm |
| July | 34°C | 22°C | 28.1°C | 66 mm | 0 cm |
| August | 34°C | 22°C | 27.8°C | 74 mm | 0 cm |
| September | 30°C | 17°C | 23.7°C | 96 mm | 0 cm |
| October | 24°C | 10°C | 17.3°C | 98 mm | 0 cm |
| November | 18°C | 4°C | 10.7°C | 59 mm | 1 cm |
| December | 12°C | −1°C | 5.6°C | 52 mm | 2 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00342660; 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 Duncan?
Normal highs sit between 65°F and 85°F in April, May and October. Of those, October has the fewest days with rain (7).
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 USC00342660.
When is the last frost in Duncan?
In Duncan, the last spring frost (32°F) comes after March 25 in half of years and after April 12 in one year in ten; the first autumn frost comes before November 7 in half of years and before October 22 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 251 year in 10 after April 12; 9 in 10 after March 3
- First autumn frost, half of years before
- November 71 year in 10 before October 22; 9 in 10 before November 23
NOAA puts the median frost-free season at 225 days, and the season without a hard freeze (28°F) at 249 days.
A hard freeze (28°F) comes after March 11 in half of springs and before November 16 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Duncan in zone 8a in ZIP code 73533. By the map's own method, the average of each year's coldest night over 1991-2020, Duncan's NOAA station is in zone 8a: the coldest night of a typical year reaches 11°F (15 complete years).
Frost dates for every NOAA station in Oklahoma · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00342660; 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 Duncan?
In a normal year in Duncan, 76 days a year reach 90°F (15 of them 100°F or more), 69 nights fall to 32°F or colder and 81 days bring measurable precipitation.
- Days at 90°F or more
- 76a normal year
- Days at 100°F or more
- 15a normal year
- Nights at 32°F or colder
- 69a normal year
- Days that stay below freezing
- 5high of 32°F or less
- Days with 0.01 inch of precipitation
- 81a normal year
- Days with 1 inch of snow or more
- 1a normal year
The highest temperature in this station's record (since 1936) is 111°F, on June 28, 1980; the lowest is −8°F, on January 3, 1947.
The wettest calendar year on that record is 2007, with 57.02 in; the snowiest season is 1965–66, with 16.4 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00342660; records: ACIS (NOAA Regional Climate Centers), station USC00342660. Records use complete months only; a month missing more than three days is left out.
How sunny is Duncan?
Over a year 80% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Duncan, 4.8 kWh per square metre a day. July is the sunniest month (88%) and February the cloudiest (72%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 77% | 2.9 |
| February | 72% | 3.5 |
| March | 74% | 4.6 |
| April | 77% | 5.6 |
| May | 76% | 6.0 |
| June | 85% | 6.9 |
| July | 88% | 6.9 |
| August | 87% | 6.3 |
| September | 83% | 5.2 |
| October | 81% | 4.0 |
| November | 79% | 3.1 |
| December | 74% | 2.5 |
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 Duncan need?
A normal year in Duncan brings 3,203 heating degree days, 40% fewer than the median U.S. place (5,373), and 2,091 cooling degree days, 2.3 times 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 5,375 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 770 | 0 |
| February | 583 | 1 |
| March | 384 | 12 |
| April | 162 | 48 |
| May | 33 | 180 |
| June | 1 | 398 |
| July | 0 | 544 |
| August | 0 | 527 |
| September | 14 | 300 |
| October | 132 | 74 |
| November | 415 | 6 |
| December | 708 | 0 |
| Year (annual) | 3,203 | 2,091 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00342660. 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.
How does Duncan's climate compare?
Duncan is warmer than 111 of the other 133 places with their own NOAA record in Oklahoma, and wetter than 51. Across the 7,247 U.S. stations with normals, its annual mean of 61.9°F is warmer than 80%.
In the Köppen classification computed from these normals, Duncan 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 Duncan share this climate record?
5 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.
- Marlow, OK4,505 people · 9 mi N
- Comanche, OK1,397 people · 10 mi S
- Central High, OK1,232 people · 11 mi NW
- Sunray, OK758 people · 6 mi S
- Empire City, OK736 people · 6 mi W
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 Duncan's climate
What is the coldest month in Duncan?
January, with a normal high of 52°F and a normal low of 28°F. The warmest is July (94°F by day, 72°F at night).
Does it snow in Duncan?
Yes: 3 inches in a normal year, falling on 2 days with 0.1 inch or more, the most in January (1.1 inches).
What is the rainiest month in Duncan?
May, with 5.58 in of precipitation in a normal year; the driest is January with 1.52 in.
What plant hardiness zone is Duncan in?
The USDA's 2023 map puts Duncan in zone 8a in ZIP code 73533. By the same method at Duncan's NOAA station, the coldest night of a typical year reaches 11°F (15 years, 1991-2020): zone 8a.
How late can frost come in Duncan?
In half of years the last 32°F night comes after March 25; in one year in ten it comes after April 12. Waiting until April 12 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Oklahoma climateThe statewide normals and every place in the state
- Velma, OK11 miles from this station, 62.3°F a year
- Acme Mesonet, OK22 miles from this station, 61.1°F a year
- Waurika, OK22 miles from this station, 64.2°F a year
- Walters, OK23 miles from this station, 62.7°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made