Lewiston, Idaho climate: Normal weather by month, frost dates and records
Lewiston's normal year runs from 30°F December nights to 91°F July afternoons, with 12.9 inches of precipitation and 13 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 12.1°C, December lows of −1°C, July highs of 33°C, 327 mm of precipitation a year.
- NOAA stationLewiston Airport
- Station IDUSW00024149
- Location46.37°N 117.02°W
- Elevation1,436 ft (438 m)
- Population34,693
On October 14, the normal high in Lewiston is 64°F and the normal low 42°F, and the chance of measurable rain or snow is 27%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Lewiston.
- Jan 42° 30°
- Feb 47° 32°
- Mar 55° 36°
- Apr 62° 41°
- May 72° 48°
- Jun 79° 54°
- Jul 91° 61°
- Aug 90° 60°
- Sep 80° 52°
- Oct 63° 42°
- Nov 49° 35°
- Dec 41° 30°
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 Lewiston each month?
July is the warmest month, with normal highs of 91°F; December the coldest, with normal lows of 30°F. The most precipitation falls in May (1.69 in), the least in July (0.47 in).
Each month has its own page with the day-by-day normals, the month's records and its recent years:
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 42°F | 30°F | 36.2°F | 1.13 | 2.7 | 11 | <1 | 18 | 9 h |
| February | 47°F | 32°F | 39.3°F | 1.04 | 3.8 | 10 | <1 | 15 | 10 h 20 min |
| March | 55°F | 36°F | 45.4°F | 1.30 | 0.8 | 12 | <1 | 9 | 11 h 50 min |
| April | 62°F | 41°F | 51.5°F | 1.44 | 0.0 | 11 | <1 | 2 | 13 h 30 min |
| May | 72°F | 48°F | 60.0°F | 1.69 | 0.0 | 11 | 1 | <1 | 15 h |
| June | 79°F | 54°F | 66.5°F | 1.25 | 0.0 | 9 | 4 | <1 | 15 h 50 min |
| July | 91°F | 61°F | 75.8°F | 0.47 | 0.0 | 4 | 18 | <1 | 15 h 30 min |
| August | 90°F | 60°F | 75.2°F | 0.51 | 0.0 | 3 | 17 | <1 | 14 h 10 min |
| September | 80°F | 52°F | 65.9°F | 0.60 | 0.0 | 5 | 4 | <1 | 12 h 40 min |
| October | 63°F | 42°F | 52.5°F | 1.08 | 0.0 | 9 | <1 | 3 | 11 h |
| November | 49°F | 35°F | 41.6°F | 1.23 | 1.3 | 11 | <1 | 12 | 9 h 30 min |
| December | 41°F | 30°F | 35.2°F | 1.13 | 4.1 | 11 | <1 | 20 | 8 h 40 min |
| Year (annual) | 64°F | 43°F | 53.8°F | 12.87 | 12.7 | 106 | 44 | 80 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 6°C | −1°C | 2.3°C | 29 mm | 7 cm |
| February | 8°C | 0°C | 4.1°C | 26 mm | 10 cm |
| March | 13°C | 2°C | 7.4°C | 33 mm | 2 cm |
| April | 17°C | 5°C | 10.8°C | 37 mm | 0 cm |
| May | 22°C | 9°C | 15.6°C | 43 mm | 0 cm |
| June | 26°C | 12°C | 19.2°C | 32 mm | 0 cm |
| July | 33°C | 16°C | 24.3°C | 12 mm | 0 cm |
| August | 32°C | 16°C | 24.0°C | 13 mm | 0 cm |
| September | 26°C | 11°C | 18.8°C | 15 mm | 0 cm |
| October | 17°C | 6°C | 11.4°C | 27 mm | 0 cm |
| November | 9°C | 1°C | 5.3°C | 31 mm | 3 cm |
| December | 5°C | −1°C | 1.8°C | 29 mm | 10 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00024149; 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 Lewiston?
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 USW00024149.
When is the last frost in Lewiston?
In Lewiston, the last spring frost (32°F) comes after April 6 in half of years and after April 26 in one year in ten; the first autumn frost comes before October 26 in half of years and before October 10 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
- April 61 year in 10 after April 26; 9 in 10 after March 20
- First autumn frost, half of years before
- October 261 year in 10 before October 10; 9 in 10 before November 12
NOAA puts the median frost-free season at 200 days, and the season without a hard freeze (28°F) at 235 days.
A hard freeze (28°F) comes after March 15 in half of springs and before November 8 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Lewiston in zone 7a in ZIP code 99179, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, Lewiston's NOAA station is in zone 7b: the coldest night of a typical year reaches 8°F (30 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 Idaho · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USW00024149; 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 Lewiston?
In a normal year in Lewiston, 44 days a year reach 90°F (9 of them 100°F or more), 80 nights fall to 32°F or colder and 106 days bring measurable precipitation.
- Days at 90°F or more
- 44a normal year
- Days at 100°F or more
- 9a normal year
- Nights at 32°F or colder
- 80a normal year
- Days that stay below freezing
- 12high of 32°F or less
- Days with 0.01 inch of precipitation
- 106a normal year
- Days with 1 inch of snow or more
- 4a normal year
The highest temperature in Lewiston's official record (kept by the National Weather Service since 1881) is 117°F, on July 27, 1939; the lowest is −23°F, on December 13, 1919.
The wettest calendar year on that record is 1884, with 21.76 in; the snowiest season is 1915–16, with 55.3 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USW00024149; records: ACIS (NOAA Regional Climate Centers), NWS threaded record LWSthr. Records use complete months only; a month missing more than three days is left out.
How humid and windy is Lewiston, and how clear are its skies?
The summer (June-August) dew point averages 45°F. The muggiest month is June, with an average dew point of 47°F; the driest air comes in December (27°F). January is the windiest month (6.1 mph on average), and July has the most clear or nearly clear hours (92%).
| Month | Dew point | Humidity | Afternoon humidity | Wind | Clear or few clouds | Overcast |
|---|---|---|---|---|---|---|
| January | 29°F | 71% | 60% | 6.1 mph | 39% | 46% |
| February | 29°F | 65% | 51% | 5.7 mph | 47% | 35% |
| March | 34°F | 60% | 43% | 5.9 mph | 49% | 29% |
| April | 37°F | 53% | 36% | 5.9 mph | 61% | 23% |
| May | 45°F | 53% | 35% | 5.4 mph | 62% | 20% |
| June | 47°F | 43% | 26% | 5.5 mph | 80% | 8% |
| July | 44°F | 32% | 19% | 5.4 mph | 92% | 3% |
| August | 43°F | 38% | 23% | 5.0 mph | 86% | 6% |
| September | 39°F | 49% | 31% | 4.6 mph | 78% | 12% |
| October | 35°F | 67% | 52% | 4.7 mph | 57% | 28% |
| November | 29°F | 74% | 66% | 5.7 mph | 41% | 45% |
| December | 27°F | 74% | 67% | 6.1 mph | 34% | 54% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00024149. Monthly averages of all hours; afternoon humidity at 3 p.m. local standard time; sky as the share of hours NOAA's observations rate clear or few clouds (a dash where NOAA publishes no sky value).
How sunny is Lewiston?
Over a year 76% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Lewiston, 4.0 kWh per square metre a day. July is the sunniest month (91%) and December the cloudiest (55%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 59% | 1.3 |
| February | 64% | 2.2 |
| March | 64% | 3.3 |
| April | 70% | 4.8 |
| May | 75% | 6.0 |
| June | 78% | 6.8 |
| July | 91% | 7.5 |
| August | 88% | 6.2 |
| September | 83% | 4.5 |
| October | 73% | 2.8 |
| November | 61% | 1.5 |
| December | 55% | 1.0 |
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 much heating and cooling does Lewiston need?
A normal year in Lewiston brings 4,980 heating degree days, 7% fewer than the median U.S. place (5,373), and 913 cooling degree days, 1% 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 3,143 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 893 | 0 |
| February | 718 | 0 |
| March | 608 | 0 |
| April | 407 | 2 |
| May | 187 | 34 |
| June | 61 | 107 |
| July | 5 | 341 |
| August | 6 | 322 |
| September | 76 | 103 |
| October | 392 | 5 |
| November | 702 | 0 |
| December | 925 | 0 |
| Year (annual) | 4,980 | 913 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00024149. 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 Lewiston been warmer than normal lately?
2025 averaged 56.1°F, 2.3°F above the 1991-2020 normal of 53.8°F. 4 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 55.8°F | +2.0°F | 8.62 | 22.2 |
| 2022 | 53.6°F | −0.2°F | 15.70 | 15.9 |
| 2023 | 55.7°F | +1.9°F | 10.81 | 3.2 |
| 2024 | 55.8°F | +2.0°F | 11.29 | 12.8 |
| 2025 | 56.1°F | +2.3°F | 10.06 | 11.6 |
Over 72 complete years from 1948 to 2025, the station's annual mean temperature rose at a fitted 3.3°F per century (+0.18°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USW00024149; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Lewiston's climate compare?
Lewiston is warmer than 82 of the other 84 places with their own NOAA record in Idaho, and wetter than 34. Across the 7,247 U.S. stations with normals, its annual mean of 53.8°F is warmer than 56%.
In the Köppen classification computed from these normals, Lewiston 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.
Which places near Lewiston share this climate record?
8 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Clarkston Heights-Vineland, WA7,144 people · 4 mi W
- Clarkston, WA7,138 people · 3 mi NW
- West Clarkston-Highland, WA5,678 people · 3 mi NW
- Lapwai, ID1,249 people · 10 mi E
- Asotin, WA1,192 people · 3 mi S
- Uniontown, WA396 people · 12 mi N
- Sweetwater, ID168 people · 10 mi E
- Anatone, WA10 people · 17 mi S
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about Lewiston's climate
What is the coldest month in Lewiston?
December, with a normal high of 41°F and a normal low of 30°F. The warmest is July (91°F by day, 61°F at night).
Does it snow in Lewiston?
Yes: 13 inches in a normal year, falling on 11 days with 0.1 inch or more, the most in December (4.1 inches).
What is the rainiest month in Lewiston?
May, with 1.69 in of precipitation in a normal year; the driest is July with 0.47 in.
What plant hardiness zone is Lewiston in?
The USDA's 2023 map puts Lewiston in zone 7a in ZIP code 99179, the nearest ZIP area. By the same method at Lewiston's NOAA station, the coldest night of a typical year reaches 8°F (30 years, 1991-2020): zone 7b.
How late can frost come in Lewiston?
In half of years the last 32°F night comes after April 6; in one year in ten it comes after April 26. Waiting until April 26 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Lewiston in OctoberThis month day by day, its records and recent years
- Idaho climateThe statewide normals and every place in the state
- Winchester, ID21 miles from this station, 44.6°F a year
- Moscow, ID25 miles from this station, 46.4°F a year
- Pullman, WA26 miles from this station, 48.6°F a year
- Pomeroy, WA28 miles from this station, 49.8°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made