Duncan, Arizona climate: Normal weather by month, frost dates and records
Duncan's normal year runs from 25°F December nights to 98°F July afternoons, with 10.4 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 16.3°C, December lows of −4°C, July highs of 36°C, 264 mm of precipitation a year.
- NOAA stationDuncan
- Station IDUSC00022754
- Location32.75°N 109.12°W
- Elevation3,660 ft (1,116 m)
- Population671
On October 23, the normal high in Duncan is 79°F and the normal low 40°F, and the chance of measurable rain or snow is 10%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Duncan.
- Jan 60° 25°
- Feb 65° 29°
- Mar 73° 33°
- Apr 81° 39°
- May 89° 47°
- Jun 98° 57°
- Jul 98° 66°
- Aug 96° 65°
- Sep 91° 56°
- Oct 81° 43°
- Nov 69° 31°
- Dec 59° 25°
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 98°F; December the coldest, with normal lows of 25°F. The most precipitation falls in August (2.18 in), the least in April (0.17 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 60°F | 25°F | 42.6°F | 0.94 | 4 | <1 | 25 | 10 h 10 min |
| February | 65°F | 29°F | 46.7°F | 0.84 | 4 | <1 | 20 | 11 h |
| March | 73°F | 33°F | 52.8°F | 0.50 | 3 | <1 | 15 | 12 h |
| April | 81°F | 39°F | 59.5°F | 0.17 | 1 | 3 | 7 | 13 h |
| May | 89°F | 47°F | 68.0°F | 0.29 | 2 | 17 | 1 | 13 h 50 min |
| June | 98°F | 57°F | 77.6°F | 0.25 | 2 | 28 | <1 | 14 h 20 min |
| July | 98°F | 66°F | 81.5°F | 1.68 | 7 | 29 | <1 | 14 h 10 min |
| August | 96°F | 65°F | 80.0°F | 2.18 | 7 | 28 | <1 | 13 h 20 min |
| September | 91°F | 56°F | 73.5°F | 1.21 | 5 | 20 | <1 | 12 h 30 min |
| October | 81°F | 43°F | 62.1°F | 0.71 | 3 | 6 | 3 | 11 h 30 min |
| November | 69°F | 31°F | 50.1°F | 0.64 | 3 | <1 | 18 | 10 h 30 min |
| December | 59°F | 25°F | 42.0°F | 1.00 | 4 | <1 | 25 | 10 h |
| Year (annual) | 80°F | 43°F | 61.4°F | 10.41 | 44 | 130 | 113 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 16°C | −4°C | 5.9°C | 24 mm |
| February | 18°C | −2°C | 8.2°C | 21 mm |
| March | 23°C | 1°C | 11.6°C | 13 mm |
| April | 27°C | 4°C | 15.3°C | 4 mm |
| May | 32°C | 8°C | 20.0°C | 7 mm |
| June | 37°C | 14°C | 25.3°C | 6 mm |
| July | 36°C | 19°C | 27.5°C | 43 mm |
| August | 35°C | 18°C | 26.7°C | 55 mm |
| September | 33°C | 14°C | 23.1°C | 31 mm |
| October | 27°C | 6°C | 16.7°C | 18 mm |
| November | 21°C | −1°C | 10.1°C | 16 mm |
| December | 15°C | −4°C | 5.6°C | 25 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Redrock (23 miles away), gets 1 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00022754; 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 March, April, October and November. Of those, April has the fewest days with rain (1).
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 USC00022754.
When is the last frost in Duncan?
In Duncan, the last spring frost (32°F) comes after April 24 in half of years and after May 8 in one year in ten; the first autumn frost comes before October 25 in half of years and before October 11 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
- April 241 year in 10 after May 8; 9 in 10 after April 8
- First autumn frost, half of years before
- October 251 year in 10 before October 11; 9 in 10 before November 5
NOAA puts the median frost-free season at 183 days, and the season without a hard freeze (28°F) at 206 days.
A hard freeze (28°F) comes after April 7 in half of springs and before November 2 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Duncan in zone 8a in ZIP code 85534, the nearest ZIP area. 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 10°F (26 complete years).
Frost dates for every NOAA station in Arizona · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00022754; 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, 130 days a year reach 90°F (40 of them 100°F or more), 113 nights fall to 32°F or colder and 44 days bring measurable precipitation.
- Days at 90°F or more
- 130a normal year
- Days at 100°F or more
- 40a normal year
- Nights at 32°F or colder
- 113a normal year
- Days that stay below freezing
- fewer than 1high of 32°F or less
- Days with 0.01 inch of precipitation
- 44a normal year
The highest temperature in this station's record (since 1901) is 113°F, on July 30, 2020; the lowest is −2°F, on January 11, 1962.
The wettest calendar year on that record is 1905, with 19.74 in; the snowiest season is 1948–49, with 15.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00022754; records: ACIS (NOAA Regional Climate Centers), station USC00022754. Records use complete months only; a month missing more than three days is left out.
How sunny is Duncan?
Over a year 89% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Duncan, 5.8 kWh per square metre a day. May is the sunniest month (94%) and February the cloudiest (85%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 86% | 3.6 |
| February | 85% | 4.5 |
| March | 89% | 6.0 |
| April | 92% | 7.4 |
| May | 94% | 8.2 |
| June | 94% | 8.2 |
| July | 86% | 7.1 |
| August | 87% | 6.6 |
| September | 88% | 5.9 |
| October | 92% | 5.1 |
| November | 89% | 3.9 |
| December | 86% | 3.3 |
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 3,091 heating degree days, 42% fewer than the median U.S. place (5,373), and 1,801 cooling degree days, 98% 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 4,911 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 693 | 0 |
| February | 512 | 0 |
| March | 379 | 1 |
| April | 179 | 15 |
| May | 37 | 130 |
| June | 1 | 380 |
| July | 0 | 512 |
| August | 0 | 467 |
| September | 4 | 260 |
| October | 126 | 36 |
| November | 449 | 1 |
| December | 711 | 0 |
| Year (annual) | 3,091 | 1,801 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00022754. 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.
Has Duncan been warmer than normal lately?
2023 averaged 62.2°F, 0.8°F above the 1991-2020 normal of 61.4°F. 2 of the 3 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 62.4°F | +1.0°F | – |
| 2022 | 61.4°F | at normal | 13.02 |
| 2023 | 62.2°F | +0.8°F | 5.72 |
Over 52 complete years from 1950 to 2024, the station's annual mean temperature rose at a fitted 3.0°F per century (+0.17°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00022754; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Duncan's climate compare?
Duncan is warmer than 32 of the other 96 places with their own NOAA record in Arizona, and wetter than 40. Across the 7,247 U.S. stations with normals, its annual mean of 61.4°F is warmer than 78%.
In the Köppen classification computed from these normals, Duncan is BSk: cold semi-arid steppe. 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?
2 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.
- Virden, NM120 people · 8 mi SE
- Franklin, AZ100 people · 6 mi SE
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?
December, with a normal high of 59°F and a normal low of 25°F. The warmest is July (98°F by day, 66°F at night).
Does it snow in Duncan?
Yes. NOAA publishes no 1991-2020 snowfall normal for Duncan's NOAA station; the nearest record that keeps one, Redrock (23 miles away), records 1 inches of snow in a normal year.
What is the rainiest month in Duncan?
August, with 2.18 in of precipitation in a normal year; the driest is April with 0.17 in.
What plant hardiness zone is Duncan in?
The USDA's 2023 map puts Duncan in zone 8a in ZIP code 85534, the nearest ZIP area. By the same method at Duncan's NOAA station, the coldest night of a typical year reaches 10°F (26 years, 1991-2020): zone 8a.
How late can frost come in Duncan?
In half of years the last 32°F night comes after April 24; in one year in ten it comes after May 8. Waiting until May 8 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Arizona climateThe statewide normals and every place in the state
- Redrock, NM23 miles from this station, 59.8°F a year
- Clifton, AZ24 miles from this station, 67.3°F a year
- Safford, AZ30 miles from this station, 66.4°F a year
- San Simon, AZ32 miles from this station, 62.9°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made