Ajo, Arizona climate: Normal weather by month, frost dates and records
Ajo's normal year runs from 43°F December nights to 104°F July afternoons, with 7.0 inches of precipitation and less than an inch of snow (0.1 in) a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 23.1°C, December lows of 6°C, July highs of 40°C, 177 mm of precipitation a year.
- NOAA stationAjo
- Station IDUSC00020080
- Location32.37°N 112.86°W
- Elevation1,751 ft (534 m)
- Population (census place)3,783
On October 23, the normal high in Ajo is 87°F and the normal low 62°F, and the chance of measurable rain or snow is 4%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Ajo.
- Jan 68° 45°
- Feb 71° 48°
- Mar 77° 52°
- Apr 84° 57°
- May 92° 66°
- Jun 101° 74°
- Jul 104° 80°
- Aug 103° 79°
- Sep 99° 74°
- Oct 89° 64°
- Nov 77° 51°
- Dec 67° 43°
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 Ajo each month?
July is the warmest month, with normal highs of 104°F; December the coldest, with normal lows of 43°F. The most precipitation falls in August (1.43 in), the least in June (0.08 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 68°F | 45°F | 56.2°F | 0.69 | 2 | <1 | 1 | 10 h 10 min |
| February | 71°F | 48°F | 59.2°F | 0.80 | 3 | <1 | <1 | 11 h |
| March | 77°F | 52°F | 64.5°F | 0.76 | 2 | 3 | <1 | 12 h |
| April | 84°F | 57°F | 70.7°F | 0.17 | 1 | 9 | <1 | 13 h |
| May | 92°F | 66°F | 78.8°F | 0.10 | 1 | 20 | <1 | 13 h 50 min |
| June | 101°F | 74°F | 87.5°F | 0.08 | <1 | 29 | <1 | 14 h 20 min |
| July | 104°F | 80°F | 91.7°F | 0.63 | 3 | 31 | <1 | 14 h 10 min |
| August | 103°F | 79°F | 91.1°F | 1.43 | 5 | 31 | <1 | 13 h 20 min |
| September | 99°F | 74°F | 86.8°F | 0.81 | 2 | 28 | <1 | 12 h 20 min |
| October | 89°F | 64°F | 76.7°F | 0.44 | 1 | 16 | <1 | 11 h 30 min |
| November | 77°F | 51°F | 64.2°F | 0.45 | 1 | 2 | <1 | 10 h 30 min |
| December | 67°F | 43°F | 55.0°F | 0.62 | 3 | <1 | 1 | 10 h |
| Year (annual) | 86°F | 61°F | 73.5°F | 6.98 | 23 | 168 | 2 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 20°C | 7°C | 13.4°C | 18 mm |
| February | 21°C | 9°C | 15.1°C | 20 mm |
| March | 25°C | 11°C | 18.1°C | 19 mm |
| April | 29°C | 14°C | 21.5°C | 4 mm |
| May | 33°C | 19°C | 26.0°C | 3 mm |
| June | 38°C | 23°C | 30.8°C | 2 mm |
| July | 40°C | 27°C | 33.2°C | 16 mm |
| August | 39°C | 26°C | 32.8°C | 36 mm |
| September | 37°C | 24°C | 30.4°C | 21 mm |
| October | 32°C | 18°C | 24.8°C | 11 mm |
| November | 25°C | 11°C | 17.9°C | 11 mm |
| December | 19°C | 6°C | 12.8°C | 16 mm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00020080; 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 Ajo?
Normal highs sit between 65°F and 85°F in January, February, March, April, November and December. Of those, November 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 USC00020080.
When is the last frost in Ajo?
In Ajo, the last spring frost (32°F) comes after January 10 in half of years and after February 15 in one year in ten; the first autumn frost comes before December 21 in half of years and before November 25 in one year in ten. A night at 32°F or colder comes at all in 81% of years here (NOAA).
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- January 101 year in 10 after February 15; 9 in 10 after December 11
- First autumn frost, half of years before
- December 211 year in 10 before November 25; 9 in 10 before January 24
NOAA puts the median frost-free season at 347 days, and the season without a hard freeze (28°F) at 365 days.
A hard freeze (28°F) comes after January 8 in half of springs and before January 3 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Ajo in zone 9b in ZIP code 85321, the nearest ZIP area.
Frost dates for every NOAA station in Arizona · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00020080; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026. 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 Ajo?
In a normal year in Ajo, 168 days a year reach 90°F (93 of them 100°F or more), 2 nights fall to 32°F or colder and 23 days bring measurable precipitation.
- Days at 90°F or more
- 168a normal year
- Days at 100°F or more
- 93a normal year
- Nights at 32°F or colder
- 2a normal year
- Days that stay below freezing
- fewer than 1high of 32°F or less
- Days with 0.01 inch of precipitation
- 23a normal year
The highest temperature in this station's record (since 1915) is 120°F, on August 7, 2025; the lowest is 17°F, on January 22, 1937.
The wettest calendar year on that record is 1978, with 14.36 in; the snowiest season is 1960–61, with 3.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00020080; records: ACIS (NOAA Regional Climate Centers), station USC00020080. Records use complete months only; a month missing more than three days is left out.
How sunny is Ajo?
Over a year 92% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Ajo, 5.9 kWh per square metre a day. June is the sunniest month (97%) and December the cloudiest (87%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 88% | 3.6 |
| February | 88% | 4.6 |
| March | 91% | 6.0 |
| April | 94% | 7.4 |
| May | 96% | 8.2 |
| June | 97% | 8.5 |
| July | 90% | 7.3 |
| August | 91% | 6.8 |
| September | 93% | 6.1 |
| October | 94% | 5.2 |
| November | 92% | 4.0 |
| December | 87% | 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 Ajo need?
A normal year in Ajo brings 1,041 heating degree days, 81% fewer than the median U.S. place (5,373), and 4,179 cooling degree days, 4.6 times the median (908). One month needs 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 8,674 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 278 | 5 |
| February | 183 | 20 |
| March | 104 | 87 |
| April | 31 | 201 |
| May | 4 | 431 |
| June | 0 | 676 |
| July | 0 | 829 |
| August | 0 | 809 |
| September | 0 | 652 |
| October | 9 | 371 |
| November | 117 | 93 |
| December | 314 | 5 |
| Year (annual) | 1,041 | 4,179 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00020080. 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 Ajo been warmer than normal lately?
2025 averaged 76.1°F, 2.6°F above the 1991-2020 normal of 73.5°F. 3 of the 3 complete years since 2022 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2022 | 74.2°F | +0.7°F | 9.30 |
| 2024 | 75.5°F | +2.0°F | 7.76 |
| 2025 | 76.1°F | +2.6°F | 4.55 |
Source: observed years: ACIS, station USC00020080. A year counts only with all twelve months complete.
How does Ajo's climate compare?
Ajo is warmer than 87 of the other 96 places with their own NOAA record in Arizona, and wetter than 14. Across the 7,247 U.S. stations with normals, its annual mean of 73.5°F is warmer than 98%.
In the Köppen classification computed from these normals, Ajo is BWh: hot desert. 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 Ajo share this climate record?
4 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.
- Why, AZ87 people · 11 mi SE
- Ventana, AZ74 people · 37 mi E
- Charco, AZ8 people · 17 mi SE
- Kaka, AZ0 people · 33 mi E
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 Ajo's climate
What is the coldest month in Ajo?
December, with a normal high of 67°F and a normal low of 43°F. The warmest is July (104°F by day, 80°F at night).
Does it snow in Ajo?
Rarely: NOAA's normal is 0.1 inch a year.
What is the rainiest month in Ajo?
August, with 1.43 in of precipitation in a normal year; the driest is June with 0.08 in.
What plant hardiness zone is Ajo in?
The USDA's 2023 map puts Ajo in zone 9b in ZIP code 85321, the nearest ZIP area.
How late can frost come in Ajo?
In half of years the last 32°F night comes after January 10; in one year in ten it comes after February 15. Waiting until February 15 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Arizona climateThe statewide normals and every place in the state
- Organ Pipe Cactus National Monument, AZ29 miles from this station, 72.0°F a year
- Gila Bend, AZ40 miles from this station, 74.7°F a year
- Painted Rock Dam, AZ50 miles from this station, 74.0°F a year
- Dateland, AZ56 miles from this station, 72.5°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made