Stewart Mountain Dam, Arizona climate: Climate normals at a NOAA weather station
Stewart Mountain Dam's normal year runs from 38°F December nights to 105°F July afternoons, with 11.9 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 21.7°C, December lows of 3°C, July highs of 41°C, 301 mm of precipitation a year.
- NOAA stationStewart Mountain Dam
- Station IDUSC00028214
- Location33.56°N 111.54°W
- Elevation1,422 ft (433 m)
On October 23, the normal high in Stewart Mountain Dam is 87°F and the normal low 53°F, and the chance of measurable rain or snow is 8%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Stewart Mountain Dam.
- Jan 69° 39°
- Feb 72° 41°
- Mar 78° 46°
- Apr 85° 50°
- May 93° 59°
- Jun 103° 68°
- Jul 105° 76°
- Aug 104° 76°
- Sep 100° 69°
- Oct 90° 56°
- Nov 78° 45°
- Dec 68° 38°
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 Stewart Mountain Dam each month?
July is the warmest month, with normal highs of 105°F; December the coldest, with normal lows of 38°F. The most precipitation falls in January (1.76 in), the least in June (0.10 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 69°F | 39°F | 53.6°F | 1.76 | 5 | <1 | 5 | 10 h 10 min |
| February | 72°F | 41°F | 56.2°F | 1.37 | 5 | <1 | 3 | 11 h |
| March | 78°F | 46°F | 61.8°F | 1.59 | 4 | 2 | <1 | 12 h |
| April | 85°F | 50°F | 67.6°F | 0.49 | 2 | 9 | <1 | 13 h |
| May | 93°F | 59°F | 76.3°F | 0.25 | 1 | 23 | <1 | 13 h 50 min |
| June | 103°F | 68°F | 85.3°F | 0.10 | 1 | 29 | <1 | 14 h 20 min |
| July | 105°F | 76°F | 90.8°F | 0.97 | 4 | 31 | <1 | 14 h 10 min |
| August | 104°F | 76°F | 90.0°F | 1.39 | 5 | 31 | <1 | 13 h 30 min |
| September | 100°F | 69°F | 84.4°F | 0.74 | 3 | 28 | <1 | 12 h 30 min |
| October | 90°F | 56°F | 73.0°F | 0.70 | 2 | 17 | <1 | 11 h 20 min |
| November | 78°F | 45°F | 61.6°F | 0.87 | 2 | 2 | 1 | 10 h 30 min |
| December | 68°F | 38°F | 53.1°F | 1.64 | 4 | <1 | 8 | 10 h |
| Year (annual) | 87°F | 55°F | 71.1°F | 11.87 | 38 | 172 | 17 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 20°C | 4°C | 12.0°C | 45 mm |
| February | 22°C | 5°C | 13.4°C | 35 mm |
| March | 26°C | 8°C | 16.6°C | 40 mm |
| April | 30°C | 10°C | 19.8°C | 12 mm |
| May | 34°C | 15°C | 24.6°C | 6 mm |
| June | 39°C | 20°C | 29.6°C | 3 mm |
| July | 41°C | 25°C | 32.7°C | 25 mm |
| August | 40°C | 24°C | 32.2°C | 35 mm |
| September | 38°C | 21°C | 29.1°C | 19 mm |
| October | 32°C | 14°C | 22.8°C | 18 mm |
| November | 26°C | 7°C | 16.4°C | 22 mm |
| December | 20°C | 3°C | 11.7°C | 42 mm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00028214; 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 Stewart Mountain Dam?
Normal highs sit between 65°F and 85°F in January, February, March, November and December. Of those, November has the fewest days with rain (2).
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 USC00028214.
When is the last frost at Stewart Mountain Dam?
In Stewart Mountain Dam, the last spring frost (32°F) comes after February 13 in half of years and after March 8 in one year in ten; the first autumn frost comes before December 5 in half of years and before November 18 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
- February 131 year in 10 after March 8; 9 in 10 after January 10
- First autumn frost, half of years before
- December 51 year in 10 before November 18; 9 in 10 before December 26
NOAA puts the median frost-free season at 295 days, and the season without a hard freeze (28°F) at 336 days.
A hard freeze (28°F) comes after January 18 in half of springs and before December 19 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Stewart Mountain Dam in zone 9b in ZIP code 85215, 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 USC00028214; 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 at Stewart Mountain Dam?
In a normal year in Stewart Mountain Dam, 172 days a year reach 90°F (101 of them 100°F or more), 17 nights fall to 32°F or colder and 38 days bring measurable precipitation.
- Days at 90°F or more
- 172a normal year
- Days at 100°F or more
- 101a normal year
- Nights at 32°F or colder
- 17a normal year
- Days that stay below freezing
- fewer than 1high of 32°F or less
- Days with 0.01 inch of precipitation
- 38a normal year
The highest temperature in this station's record (since 1961) is 120°F, on June 27, 1990; the lowest is 17°F, on January 8, 1971.
The wettest calendar year on that record is 1992, with 24.11 in.
Source: NOAA NCEI 1991-2020 annual normals, station USC00028214; records: ACIS (NOAA Regional Climate Centers), station USC00028214. Records use complete months only; a month missing more than three days is left out.
How sunny is it at Stewart Mountain Dam?
Over a year 91% of the sunlight that would reach the ground under clear skies gets through the clouds at Stewart Mountain Dam, 5.8 kWh per square metre a day. June is the sunniest month (97%) and December the cloudiest (84%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 85% | 3.4 |
| February | 84% | 4.3 |
| March | 89% | 5.8 |
| April | 93% | 7.3 |
| May | 95% | 8.2 |
| June | 97% | 8.5 |
| July | 91% | 7.4 |
| August | 91% | 6.8 |
| September | 93% | 6.1 |
| October | 93% | 5.0 |
| November | 89% | 3.8 |
| December | 84% | 3.0 |
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 Stewart Mountain Dam record?
A normal year at Stewart Mountain Dam brings 1,318 heating degree days, 75% fewer than the median U.S. place (5,373), and 3,589 cooling degree days, 4.0 times the median (908). Two months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 7,825 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 354 | 0 |
| February | 248 | 3 |
| March | 135 | 36 |
| April | 42 | 120 |
| May | 5 | 355 |
| June | 0 | 609 |
| July | 0 | 800 |
| August | 0 | 773 |
| September | 0 | 582 |
| October | 16 | 264 |
| November | 148 | 44 |
| December | 370 | 1 |
| Year (annual) | 1,318 | 3,589 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00028214. 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 Stewart Mountain Dam's climate compare?
Stewart Mountain Dam is warmer than 71 of the 97 places with their own NOAA record in Arizona, and wetter than 50. Across the 7,247 U.S. stations with normals, its annual mean of 71.1°F is warmer than 96%.
In the Köppen classification computed from these normals, Stewart Mountain Dam is BSh: hot 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.
Questions about Stewart Mountain Dam's climate
What is the coldest month at Stewart Mountain Dam?
December, with a normal high of 68°F and a normal low of 38°F. The warmest is July (105°F by day, 76°F at night).
Does it snow at Stewart Mountain Dam?
Rarely: NOAA's normal is no measurable snow a year.
What is the rainiest month at Stewart Mountain Dam?
January, with 1.76 in of precipitation in a normal year; the driest is June with 0.10 in.
What plant hardiness zone is Stewart Mountain Dam in?
The USDA's 2023 map puts Stewart Mountain Dam in zone 9b in ZIP code 85215, the nearest ZIP area.
How late can frost come at Stewart Mountain Dam?
In half of years the last 32°F night comes after February 13; in one year in ten it comes after March 8. Waiting until March 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
- Mormon Flat, AZ6 miles from this station, 73.2°F a year
- Apache Junction, AZ7 miles from this station, 71.9°F a year
- Fountain Hills, AZ11 miles from this station, 72.1°F a year
- Mesa, AZ11 miles from this station, 72.2°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made