American Falls, Idaho climate: Normal weather by month, frost dates and records
American Falls's normal year runs from 19°F January nights to 90°F July afternoons, with 11.1 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 9.3°C, January lows of −7°C, July highs of 32°C, 282 mm of precipitation a year.
- NOAA stationAmerican Falls
- Station IDUSC00100218
- Location42.80°N 112.80°W
- Elevation4,510 ft (1,375 m)
- Population4,863
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for American Falls.
- Jan 35° 19°
- Feb 39° 21°
- Mar 52° 29°
- Apr 60° 35°
- May 71° 43°
- Jun 79° 50°
- Jul 90° 56°
- Aug 88° 55°
- Sep 77° 46°
- Oct 61° 36°
- Nov 47° 27°
- Dec 35° 20°
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 American Falls each month?
July is the warmest month, with normal highs of 90°F; January the coldest, with normal lows of 19°F. The most precipitation falls in May (1.54 in), the least in August (0.49 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 35°F | 19°F | 26.6°F | 0.96 | 8 | <1 | 28 | 9 h 20 min |
| February | 39°F | 21°F | 30.0°F | 0.68 | 7 | <1 | 23 | 10 h 30 min |
| March | 52°F | 29°F | 40.5°F | 1.02 | 9 | <1 | 20 | 11 h 50 min |
| April | 60°F | 35°F | 47.5°F | 1.30 | 9 | <1 | 11 | 13 h 20 min |
| May | 71°F | 43°F | 56.9°F | 1.54 | 8 | <1 | 3 | 14 h 40 min |
| June | 79°F | 50°F | 64.4°F | 1.15 | 5 | 6 | <1 | 15 h 20 min |
| July | 90°F | 56°F | 73.4°F | 0.53 | 3 | 20 | <1 | 15 h |
| August | 88°F | 55°F | 71.2°F | 0.49 | 3 | 14 | <1 | 14 h |
| September | 77°F | 46°F | 61.5°F | 0.81 | 5 | 2 | <1 | 12 h 30 min |
| October | 61°F | 36°F | 48.8°F | 0.92 | 6 | <1 | 10 | 11 h 10 min |
| November | 47°F | 27°F | 36.6°F | 0.83 | 6 | <1 | 22 | 9 h 50 min |
| December | 35°F | 20°F | 27.2°F | 0.87 | 9 | <1 | 28 | 9 h |
| Year (annual) | 61°F | 36°F | 48.7°F | 11.10 | 77 | 42 | 145 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 1°C | −7°C | −3.0°C | 24 mm |
| February | 4°C | −6°C | −1.1°C | 17 mm |
| March | 11°C | −2°C | 4.7°C | 26 mm |
| April | 16°C | 2°C | 8.6°C | 33 mm |
| May | 22°C | 6°C | 13.8°C | 39 mm |
| June | 26°C | 10°C | 18.0°C | 29 mm |
| July | 32°C | 14°C | 23.0°C | 13 mm |
| August | 31°C | 13°C | 21.8°C | 12 mm |
| September | 25°C | 8°C | 16.4°C | 21 mm |
| October | 16°C | 2°C | 9.3°C | 23 mm |
| November | 8°C | −3°C | 2.6°C | 21 mm |
| December | 1°C | −7°C | −2.7°C | 22 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. American Falls's own co-op station American Falls (6 mi NE) does: 35 inches of snow in a normal year (see the other stations below).
Source: NOAA NCEI 1991-2020 monthly normals, station USC00100218; 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 American Falls?
Normal highs sit between 65°F and 85°F in May, June and September. Of those, September has the fewest days with rain (5).
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 USC00100218.
When is the last frost in American Falls?
In American Falls, the last spring frost (32°F) comes after May 4 in half of years and after May 21 in one year in ten; the first autumn frost comes before October 8 in half of years and before September 22 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 41 year in 10 after May 21; 9 in 10 after April 20
- First autumn frost, half of years before
- October 81 year in 10 before September 22; 9 in 10 before October 24
NOAA puts the median frost-free season at 155 days, and the season without a hard freeze (28°F) at 185 days.
A hard freeze (28°F) comes after April 19 in half of springs and before October 21 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts American Falls in zone 6a in ZIP code 83211, 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 USC00100218; 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 American Falls?
In a normal year in American Falls, 42 days a year reach 90°F (2 of them 100°F or more), 145 nights fall to 32°F or colder and 77 days bring measurable precipitation.
- Days at 90°F or more
- 42a normal year
- Days at 100°F or more
- 2a normal year
- Nights at 32°F or colder
- 145a normal year
- Days that stay below freezing
- 30high of 32°F or less
- Days with 0.01 inch of precipitation
- 77a normal year
The highest temperature in American Falls's official record (kept by the National Weather Service since 1892) is 106°F, on July 14, 1925; the lowest is −38°F, on January 25, 1949.
The wettest calendar year on that record is 1983, with 21.88 in; the snowiest season is 2016–17, with 78.1 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00100218; records: ACIS (NOAA Regional Climate Centers), NWS threaded record AFLI1thr. Records use complete months only; a month missing more than three days is left out.
How sunny is American Falls?
Over a year 78% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around American Falls, 4.5 kWh per square metre a day. July is the sunniest month (88%) and December the cloudiest (60%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 67% | 1.9 |
| February | 68% | 2.8 |
| March | 71% | 4.0 |
| April | 72% | 5.3 |
| May | 77% | 6.5 |
| June | 84% | 7.5 |
| July | 88% | 7.5 |
| August | 88% | 6.6 |
| September | 85% | 5.2 |
| October | 79% | 3.5 |
| November | 69% | 2.1 |
| December | 60% | 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 American Falls need?
A normal year in American Falls brings 6,507 heating degree days, 21% more than the median U.S. place (5,373), and 608 cooling degree days, 33% fewer 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 2,554 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,190 | 0 |
| February | 978 | 0 |
| March | 761 | 0 |
| April | 525 | 0 |
| May | 266 | 15 |
| June | 97 | 77 |
| July | 7 | 267 |
| August | 15 | 208 |
| September | 142 | 39 |
| October | 504 | 2 |
| November | 851 | 0 |
| December | 1,170 | 0 |
| Year (annual) | 6,507 | 608 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00100218. 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 American Falls been warmer than normal lately?
2024 averaged 50.3°F, 1.6°F above the 1991-2020 normal of 48.7°F. 2 of the 4 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 51.3°F | +2.6°F | 10.65 |
| 2022 | 47.3°F | −1.4°F | 10.64 |
| 2023 | 47.5°F | −1.2°F | 15.68 |
| 2024 | 50.3°F | +1.6°F | 16.56 |
Source: observed years: ACIS, station USC00100218. A year counts only with all twelve months complete.
How does American Falls's climate compare?
American Falls is warmer than 60 of the other 84 places with their own NOAA record in Idaho, and wetter than 26. Across the 7,247 U.S. stations with normals, its annual mean of 48.7°F is warmer than 35%.
In the Köppen classification computed from these normals, American Falls 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.
What do American Falls's other NOAA stations record?
One more NOAA station keeps 1991-2020 normals in or near American Falls. This page uses American Falls; the other differs by site and elevation:
| Station | From this station | Elevation | Year | Jan low | Jul high | Precip. | Snow | Last frost |
|---|---|---|---|---|---|---|---|---|
| American Falls (6 mi NE) USC00100227 | 6 mi NW | 4,415 ft | 46.7°F | 17°F | 85°F | 11.1 | 35 | May 14 |
Source: NOAA NCEI 1991-2020 normals for each station. Last frost: the median last spring date of 32°F.
Questions about American Falls's climate
What is the coldest month in American Falls?
January, with a normal high of 35°F and a normal low of 19°F. The warmest is July (90°F by day, 56°F at night).
Does it snow in American Falls?
Yes. NOAA publishes no 1991-2020 snowfall normal for American Falls's NOAA station; American Falls's own co-op station American Falls (6 mi NE) records 35 inches of snow in a normal year.
What is the rainiest month in American Falls?
May, with 1.54 in of precipitation in a normal year; the driest is August with 0.49 in.
What plant hardiness zone is American Falls in?
The USDA's 2023 map puts American Falls in zone 6a in ZIP code 83211, the nearest ZIP area.
How late can frost come in American Falls?
In half of years the last 32°F night comes after May 4; in one year in ten it comes after May 21. Waiting until May 21 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Idaho climateThe statewide normals and every place in the state
- Aberdeen, ID11 miles from this station, 45.4°F a year
- Massacre Rocks State Park, ID14 miles from this station, 47.3°F a year
- Pocatello, ID14 miles from this station, 47.0°F a year
- Fort Hall, ID26 miles from this station, 45.4°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made