Fairfield weather by month
What a typical year looks like in Fairfield, Idaho: average highs and lows, rain and snow, and the warmest and coldest days on record. Normals are the 1991–2020 averages at Fairfield Ranger Station, 1 km from Fairfield; records cover 1948–2026.
The year at a glance
- Precipitation a year
- 14.6 in370 mm
- Snow a year
- Rare
- Last spring freeze
- Jun 16
- First fall freeze
- Sep 6
- Heating degree days
- 8,521
- Cooling degree days
- 216
Freeze dates are medians (half of years earlier, half later). Degree days use a 65°F base; HVAC design temperatures here are −16°−27° (heating, 99%) and 94°34° (cooling, 1%).
Month by month
Fairfield in January
Highs average 27°−3° and lows 9°−13°, with 2.1 in54 mm of precipitation in a typical January.
- Record high
- 50°10° (2026)
- Record low
- −42°−41° (1984)
- Heating degree days
- 1449
- Cooling degree days
- 0
Fairfield in February
Highs average 31°0° and lows 12°−11°, with 1.5 in38 mm of precipitation in a typical February.
- Record high
- 63°17° (1992)
- Record low
- −38°−39° (1950)
- Heating degree days
- 1218
- Cooling degree days
- 0
Fairfield in March
Highs average 41°5° and lows 21°−6°, with 1.6 in41 mm of precipitation in a typical March.
- Record high
- 75°24° (2026)
- Record low
- −24°−31° (1955)
- Heating degree days
- 1065
- Cooling degree days
- 0
Fairfield in April
Highs average 54°12° and lows 30°−1°, with 1.1 in28 mm of precipitation in a typical April.
- Record high
- 83°28° (1987)
- Record low
- −3°−19° (1967)
- Heating degree days
- 692
- Cooling degree days
- 0
Fairfield in May
Highs average 65°18° and lows 38°3°, with 1.6 in41 mm of precipitation in a typical May.
- Record high
- 94°34° (2003)
- Record low
- 15°−9° (1968)
- Heating degree days
- 426
- Cooling degree days
- 1
Fairfield in June
Highs average 73°23° and lows 43°6°, with 0.85 in22 mm of precipitation in a typical June.
- Record high
- 99°37° (1949)
- Record low
- 19°−7° (1966)
- Heating degree days
- 222
- Cooling degree days
- 16
Fairfield in July
Highs average 84°29° and lows 50°10°, with 0.38 in9.7 mm of precipitation in a typical July.
- Record high
- 101°38° (2002)
- Record low
- 26°−3° (1981)
- Heating degree days
- 47
- Cooling degree days
- 110
Fairfield in August
Highs average 83°28° and lows 48°9°, with 0.35 in8.9 mm of precipitation in a typical August.
- Record high
- 101°38° (2012)
- Record low
- 23°−5° (1992)
- Heating degree days
- 62
- Cooling degree days
- 79
Fairfield in September
Highs average 74°23° and lows 40°4°, with 0.7 in18 mm of precipitation in a typical September.
- Record high
- 96°36° (1950)
- Record low
- 11°−12° (1985)
- Heating degree days
- 260
- Cooling degree days
- 10
Fairfield in OctoberThis month
Highs average 59°15° and lows 30°−1°, with 0.97 in25 mm of precipitation in a typical October.
- Record high
- 87°31° (1992)
- Record low
- −16°−27° (2019)
- Heating degree days
- 634
- Cooling degree days
- 0
Fairfield in November
Highs average 42°5° and lows 20°−6°, with 1.4 in35 mm of precipitation in a typical November.
- Record high
- 69°21° (1949)
- Record low
- −21°−29° (1955)
- Heating degree days
- 1020
- Cooling degree days
- 0
Fairfield in December
Highs average 28°−2° and lows 10°−12°, with 2 in50 mm of precipitation in a typical December.
- Record high
- 58°14° (2008)
- Record low
- −40° (1983)
- Heating degree days
- 1426
- Cooling degree days
- 0