St. Johns, Arizona climate: Normal weather by month, frost dates and records
St. Johns's normal year runs from 18°F December nights to 91°F July afternoons, with 9.1 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 12.3°C, December lows of −8°C, July highs of 33°C, 231 mm of precipitation a year.
- NOAA stationSt Johns Industrial Airport
- Station IDUSW00093027
- Location34.52°N 109.38°W
- Elevation5,733 ft (1,747 m)
- Population3,352
On October 14, the normal high in St. Johns is 73°F and the normal low 37°F, and the chance of measurable rain or snow is 14%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for St. Johns.
- Jan 50° 19°
- Feb 55° 23°
- Mar 62° 28°
- Apr 70° 35°
- May 79° 44°
- Jun 90° 53°
- Jul 91° 61°
- Aug 88° 59°
- Sep 83° 50°
- Oct 72° 37°
- Nov 60° 26°
- Dec 49° 18°
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 St. Johns each month?
July is the warmest month, with normal highs of 91°F; December the coldest, with normal lows of 18°F. The most precipitation falls in August (2.08 in), the least in June (0.18 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 50°F | 19°F | 34.4°F | 0.43 | 5 | <1 | 28 | 10 h |
| February | 55°F | 23°F | 38.6°F | 0.53 | 4 | <1 | 24 | 11 h |
| March | 62°F | 28°F | 45.1°F | 0.43 | 4 | <1 | 20 | 11 h 50 min |
| April | 70°F | 35°F | 52.3°F | 0.29 | 3 | <1 | 9 | 13 h |
| May | 79°F | 44°F | 61.4°F | 0.43 | 3 | 3 | 2 | 14 h |
| June | 90°F | 53°F | 71.5°F | 0.18 | 2 | 20 | <1 | 14 h 30 min |
| July | 91°F | 61°F | 75.9°F | 1.41 | 10 | 20 | <1 | 14 h 20 min |
| August | 88°F | 59°F | 73.2°F | 2.08 | 11 | 14 | <1 | 13 h 30 min |
| September | 83°F | 50°F | 66.6°F | 1.13 | 6 | 4 | <1 | 12 h 30 min |
| October | 72°F | 37°F | 54.4°F | 0.69 | 5 | <1 | 7 | 11 h 20 min |
| November | 60°F | 26°F | 42.7°F | 0.61 | 3 | <1 | 23 | 10 h 20 min |
| December | 49°F | 18°F | 33.6°F | 0.88 | 5 | <1 | 29 | 9 h 50 min |
| Year (annual) | 71°F | 38°F | 54.2°F | 9.09 | 61 | 61 | 142 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 10°C | −7°C | 1.3°C | 11 mm |
| February | 13°C | −5°C | 3.7°C | 13 mm |
| March | 17°C | −2°C | 7.3°C | 11 mm |
| April | 21°C | 2°C | 11.3°C | 7 mm |
| May | 26°C | 6°C | 16.3°C | 11 mm |
| June | 32°C | 12°C | 21.9°C | 5 mm |
| July | 33°C | 16°C | 24.4°C | 36 mm |
| August | 31°C | 15°C | 22.9°C | 53 mm |
| September | 28°C | 10°C | 19.2°C | 29 mm |
| October | 22°C | 3°C | 12.4°C | 18 mm |
| November | 15°C | −3°C | 5.9°C | 15 mm |
| December | 9°C | −8°C | 0.9°C | 22 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Saint Johns station (1 miles away), gets 6 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USW00093027; 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 St. Johns?
Normal highs sit between 65°F and 85°F in April, May, September and October. Of those, May has the fewest days with rain (3).
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 USW00093027.
When is the last frost in St. Johns?
In St. Johns, the last spring frost (32°F) comes after May 3 in half of years and after May 19 in one year in ten; the first autumn frost comes before October 10 in half of years and before September 30 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
- May 31 year in 10 after May 19; 9 in 10 after April 20
- First autumn frost, half of years before
- October 101 year in 10 before September 30; 9 in 10 before October 25
NOAA puts the median frost-free season at 160 days, and the season without a hard freeze (28°F) at 180 days.
A hard freeze (28°F) comes after April 21 in half of springs and before October 20 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts St. Johns in zone 6b in ZIP code 85936, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, St. Johns's NOAA station is in zone 7a: the coldest night of a typical year reaches 0°F (21 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 Arizona · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USW00093027; 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 St. Johns?
In a normal year in St. Johns, 61 days a year reach 90°F (3 of them 100°F or more), 142 nights fall to 32°F or colder and 61 days bring measurable precipitation.
- Days at 90°F or more
- 61a normal year
- Days at 100°F or more
- 3a normal year
- Nights at 32°F or colder
- 142a normal year
- Days that stay below freezing
- 3high of 32°F or less
- Days with 0.01 inch of precipitation
- 61a normal year
The highest temperature in this station's record (since 1999) is 107°F, on July 18, 2005; the lowest is −22°F, on January 1, 2011.
The wettest calendar year on that record is 2021, with 11.36 in.
Source: NOAA NCEI 1991-2020 annual normals, station USW00093027; records: ACIS (NOAA Regional Climate Centers), station USW00093027. Records use complete months only; a month missing more than three days is left out.
How sunny is St. Johns?
Over a year 86% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around St. Johns, 5.6 kWh per square metre a day. June is the sunniest month (91%) and July the cloudiest (80%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 82% | 3.3 |
| February | 82% | 4.2 |
| March | 86% | 5.7 |
| April | 89% | 7.1 |
| May | 90% | 7.9 |
| June | 91% | 8.3 |
| July | 80% | 6.8 |
| August | 82% | 6.4 |
| September | 87% | 5.9 |
| October | 90% | 4.9 |
| November | 87% | 3.7 |
| December | 81% | 2.9 |
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 much heating and cooling does St. Johns need?
A normal year in St. Johns brings 4,861 heating degree days, 10% fewer than the median U.S. place (5,373), and 932 cooling degree days, 3% more than the median (908). Seven months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 3,361 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 947 | 0 |
| February | 738 | 0 |
| March | 615 | 0 |
| April | 382 | 1 |
| May | 152 | 40 |
| June | 11 | 204 |
| July | 0 | 336 |
| August | 1 | 255 |
| September | 42 | 92 |
| October | 332 | 4 |
| November | 668 | 0 |
| December | 973 | 0 |
| Year (annual) | 4,861 | 932 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00093027. 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 St. Johns been warmer than normal lately?
2021 averaged 55.4°F, 1.2°F above the 1991-2020 normal of 54.2°F.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 55.4°F | +1.2°F | 11.36 |
Source: observed years: ACIS, station USW00093027. A year counts only with all twelve months complete.
How does St. Johns's climate compare?
St. Johns is warmer than 16 of the other 96 places with their own NOAA record in Arizona, and wetter than 34. Across the 7,247 U.S. stations with normals, its annual mean of 54.2°F is warmer than 58%.
In the Köppen classification computed from these normals, St. Johns 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.
Questions about St. Johns's climate
What is the coldest month in St. Johns?
December, with a normal high of 49°F and a normal low of 18°F. The warmest is July (91°F by day, 61°F at night).
Does it snow in St. Johns?
Yes. NOAA publishes no 1991-2020 snowfall normal for St. Johns's NOAA station; the nearest record that keeps one, Saint Johns station (1 miles away), records 6 inches of snow in a normal year.
What is the rainiest month in St. Johns?
August, with 2.08 in of precipitation in a normal year; the driest is June with 0.18 in.
What plant hardiness zone is St. Johns in?
The USDA's 2023 map puts St. Johns in zone 6b in ZIP code 85936, the nearest ZIP area. By the same method at St. Johns's NOAA station, the coldest night of a typical year reaches 0°F (21 years, 1991-2020): zone 7a.
How late can frost come in St. Johns?
In half of years the last 32°F night comes after May 3; in one year in ten it comes after May 19. Waiting until May 19 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Arizona climateThe statewide normals and every place in the state
- Saint Johns station, AZ1 miles from this station, 54.7°F a year
- Springerville, AZ27 miles from this station, 50.2°F a year
- Greer, AZ35 miles from this station, 44.2°F a year
- Petrified Forest National Park, AZ35 miles from this station, 55.6°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made