Fairfield, Idaho climate: Normal weather by month, frost dates and records
Fairfield's normal year runs from 9°F January nights to 84°F July afternoons, with 14.6 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 5.6°C, January lows of −13°C, July highs of 29°C, 370 mm of precipitation a year.
- NOAA stationFairfield Ranger Station
- Station IDUSC00103108
- Location43.34°N 114.79°W
- Elevation5,065 ft (1,544 m)
- Population484
On October 14, the normal high in Fairfield is 60°F and the normal low 31°F.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Fairfield.
- Jan 27° 9°
- Feb 31° 12°
- Mar 41° 21°
- Apr 54° 30°
- May 65° 38°
- Jun 73° 43°
- Jul 84° 50°
- Aug 83° 48°
- Sep 74° 40°
- Oct 59° 30°
- Nov 42° 20°
- Dec 28° 10°
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 Fairfield each month?
July is the warmest month, with normal highs of 84°F; January the coldest, with normal lows of 9°F. The most precipitation falls in January (2.11 in), the least in August (0.35 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 27°F | 9°F | 18.3°F | 2.11 | – | <1 | 31 | 9 h 20 min |
| February | 31°F | 12°F | 21.5°F | 1.50 | – | <1 | 27 | 10 h 30 min |
| March | 41°F | 21°F | 30.7°F | 1.61 | – | <1 | 29 | 11 h 50 min |
| April | 54°F | 30°F | 42.0°F | 1.11 | – | <1 | 20 | 13 h 20 min |
| May | 65°F | 38°F | 51.3°F | 1.60 | – | <1 | 9 | 14 h 40 min |
| June | 73°F | 43°F | 58.2°F | 0.85 | – | 1 | 3 | 15 h 20 min |
| July | 84°F | 50°F | 67.0°F | 0.38 | – | 10 | <1 | 15 h 10 min |
| August | 83°F | 48°F | 65.5°F | 0.35 | – | 8 | 1 | 14 h |
| September | 74°F | 40°F | 56.7°F | 0.70 | – | 1 | 6 | 12 h 30 min |
| October | 59°F | 30°F | 44.5°F | 0.97 | – | <1 | 20 | 11 h 10 min |
| November | 42°F | 20°F | 31.0°F | 1.39 | – | <1 | 28 | 9 h 40 min |
| December | 28°F | 10°F | 19.0°F | 1.98 | – | <1 | 31 | 9 h |
| Year (annual) | 55°F | 29°F | 42.1°F | 14.55 | – | 19 | 204 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | −3°C | −13°C | −7.6°C | 54 mm |
| February | 0°C | −11°C | −5.8°C | 38 mm |
| March | 5°C | −6°C | −0.7°C | 41 mm |
| April | 12°C | −1°C | 5.6°C | 28 mm |
| May | 18°C | 3°C | 10.7°C | 41 mm |
| June | 23°C | 6°C | 14.6°C | 22 mm |
| July | 29°C | 10°C | 19.4°C | 10 mm |
| August | 28°C | 9°C | 18.6°C | 9 mm |
| September | 23°C | 4°C | 13.7°C | 18 mm |
| October | 15°C | −1°C | 6.9°C | 25 mm |
| November | 5°C | −6°C | −0.6°C | 35 mm |
| December | −2°C | −12°C | −7.2°C | 50 mm |
NOAA publishes no 1991-2020 snowfall normal for this station, and no record within 25 miles keeps one, so snow is left out here rather than estimated.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00103108; 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 Fairfield?
Normal highs sit between 65°F and 85°F in June, July, August and September.
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 USC00103108.
When is the last frost in Fairfield?
In Fairfield, the last spring frost (32°F) comes after June 8 in half of years and after June 28 in one year in ten; the first autumn frost comes before September 14 in half of years and before August 29 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
- June 81 year in 10 after June 28; 9 in 10 after May 15
- First autumn frost, half of years before
- September 141 year in 10 before August 29; 9 in 10 before September 28
NOAA puts the median frost-free season at 97 days, and the season without a hard freeze (28°F) at 134 days.
A hard freeze (28°F) comes after May 11 in half of springs and before September 28 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Fairfield in zone 5a in ZIP code 83322, the nearest ZIP area.
Frost dates for every NOAA station in Idaho · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00103108; 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 Fairfield?
In a normal year in Fairfield, 19 days a year reach 90°F and 204 nights fall to 32°F or colder.
- Days at 90°F or more
- 19a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 204a normal year
- Days that stay below freezing
- 55high of 32°F or less
The highest temperature in this station's record (since 1948) is 100°F, on July 22, 2006; the lowest is −42°F, on January 19, 1984.
The wettest calendar year on that record is 1983, with 26.79 in; the snowiest season is 1951–52, with 180.7 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00103108; records: ACIS (NOAA Regional Climate Centers), station USC00103108. Records use complete months only; a month missing more than three days is left out.
How sunny is Fairfield?
Over a year 80% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Fairfield, 4.6 kWh per square metre a day. July is the sunniest month (90%) and December the cloudiest (66%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 72% | 2.0 |
| February | 72% | 2.9 |
| March | 72% | 4.1 |
| April | 74% | 5.4 |
| May | 76% | 6.4 |
| June | 84% | 7.5 |
| July | 90% | 7.7 |
| August | 89% | 6.6 |
| September | 86% | 5.1 |
| October | 80% | 3.5 |
| November | 72% | 2.1 |
| December | 66% | 1.5 |
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 Fairfield need?
A normal year in Fairfield brings 8,520 heating degree days, 59% more than the median U.S. place (5,373), and 216 cooling degree days, 76% fewer than the median (908). Eight months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 1,663 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,449 | 0 |
| February | 1,218 | 0 |
| March | 1,065 | 0 |
| April | 692 | 0 |
| May | 426 | 1 |
| June | 222 | 16 |
| July | 47 | 110 |
| August | 62 | 79 |
| September | 260 | 10 |
| October | 634 | 0 |
| November | 1,020 | 0 |
| December | 1,426 | 0 |
| Year (annual) | 8,520 | 216 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00103108. 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 Fairfield been warmer than normal lately?
2025 averaged 43.4°F, 1.3°F above the 1991-2020 normal of 42.1°F. 2 of the 2 complete years since 2024 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2024 | 43.0°F | +0.9°F | 13.07 |
| 2025 | 43.4°F | +1.3°F | – |
Source: observed years: ACIS, station USC00103108. A year counts only with all twelve months complete.
How does Fairfield's climate compare?
Fairfield is warmer than 8 of the other 84 places with their own NOAA record in Idaho, and wetter than 39. Across the 7,247 U.S. stations with normals, its annual mean of 42.1°F is warmer than 10%.
In the Köppen classification computed from these normals, Fairfield is Dsb: continental, dry-summer, warm 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.
Questions about Fairfield's climate
What is the coldest month in Fairfield?
January, with a normal high of 27°F and a normal low of 9°F. The warmest is July (84°F by day, 50°F at night).
What is the rainiest month in Fairfield?
January, with 2.11 in of precipitation in a normal year; the driest is August with 0.35 in.
What plant hardiness zone is Fairfield in?
The USDA's 2023 map puts Fairfield in zone 5a in ZIP code 83322, the nearest ZIP area.
How late can frost come in Fairfield?
In half of years the last 32°F night comes after June 8; in one year in ten it comes after June 28. Waiting until June 28 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Idaho climateThe statewide normals and every place in the state
- Hill City (1 mi W), ID14 miles from this station, 42.1°F a year
- Bellevue, ID28 miles from this station, 46.9°F a year
- Ketchum, ID32 miles from this station, 40.2°F a year
- Shoshone, ID34 miles from this station, 52.7°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made