Idaho City, Idaho climate: Normal weather by month, frost dates and records
Idaho City's normal year runs from 14°F December nights to 87°F July afternoons, with 21.1 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 6.6°C, December lows of −10°C, July highs of 31°C, 536 mm of precipitation a year.
- NOAA stationIdaho City
- Station IDUSC00104442
- Location43.84°N 115.83°W
- Elevation3,965 ft (1,209 m)
- Population536
On October 23, the normal high in Idaho City is 57°F and the normal low 26°F, and the chance of measurable rain or snow is 21%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Idaho City.
- Jan 35° 14°
- Feb 41° 16°
- Mar 48° 22°
- Apr 56° 28°
- May 66° 35°
- Jun 75° 40°
- Jul 87° 46°
- Aug 86° 44°
- Sep 77° 36°
- Oct 62° 28°
- Nov 44° 21°
- Dec 35° 14°
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 Idaho City each month?
July is the warmest month, with normal highs of 87°F; December the coldest, with normal lows of 14°F. The most precipitation falls in December (3.53 in), the least in July (0.32 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 35°F | 14°F | 24.4°F | 3.16 | 11 | <1 | 31 | 9 h 20 min |
| February | 41°F | 16°F | 28.2°F | 1.94 | 8 | <1 | 28 | 10 h 30 min |
| March | 48°F | 22°F | 34.9°F | 2.26 | 10 | <1 | 30 | 11 h 50 min |
| April | 56°F | 28°F | 41.7°F | 1.59 | 10 | <1 | 24 | 13 h 20 min |
| May | 66°F | 35°F | 50.5°F | 2.11 | 8 | <1 | 12 | 14 h 40 min |
| June | 75°F | 40°F | 57.8°F | 1.09 | 7 | 2 | 4 | 15 h 30 min |
| July | 87°F | 46°F | 66.3°F | 0.32 | 3 | 13 | <1 | 15 h 10 min |
| August | 86°F | 44°F | 65.0°F | 0.44 | 2 | 13 | 1 | 14 h |
| September | 77°F | 36°F | 56.1°F | 0.77 | 3 | 2 | 10 | 12 h 30 min |
| October | 62°F | 28°F | 44.5°F | 1.50 | 6 | <1 | 26 | 11 h 10 min |
| November | 44°F | 21°F | 32.5°F | 2.41 | 9 | <1 | 28 | 9 h 40 min |
| December | 35°F | 14°F | 24.3°F | 3.53 | 12 | <1 | 31 | 9 h |
| Year (annual) | 59°F | 28°F | 43.8°F | 21.12 | 88 | 31 | 224 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 2°C | −10°C | −4.2°C | 80 mm |
| February | 5°C | −9°C | −2.1°C | 49 mm |
| March | 9°C | −6°C | 1.6°C | 57 mm |
| April | 13°C | −2°C | 5.4°C | 40 mm |
| May | 19°C | 1°C | 10.3°C | 54 mm |
| June | 24°C | 5°C | 14.3°C | 28 mm |
| July | 31°C | 8°C | 19.1°C | 8 mm |
| August | 30°C | 6°C | 18.3°C | 11 mm |
| September | 25°C | 2°C | 13.4°C | 20 mm |
| October | 16°C | −2°C | 6.9°C | 38 mm |
| November | 7°C | −6°C | 0.3°C | 61 mm |
| December | 1°C | −10°C | −4.3°C | 90 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Garden Valley (19 miles away), gets 69 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00104442; 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 Idaho City?
Normal highs sit between 65°F and 85°F in May, June and September. Of those, September 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 USC00104442.
When is the last frost in Idaho City?
In Idaho City, the last spring frost (32°F) comes after June 17 in half of years and after July 4 in one year in ten; the first autumn frost comes before September 5 in half of years and before August 23 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 171 year in 10 after July 4; 9 in 10 after May 30
- First autumn frost, half of years before
- September 51 year in 10 before August 23; 9 in 10 before September 21
NOAA puts the median frost-free season at 80 days, and the season without a hard freeze (28°F) at 117 days.
A hard freeze (28°F) comes after May 22 in half of springs and before September 19 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Idaho City in zone 6b in ZIP code 83631, 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 USC00104442; 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 Idaho City?
In a normal year in Idaho City, 31 days a year reach 90°F (2 of them 100°F or more), 224 nights fall to 32°F or colder and 88 days bring measurable precipitation.
- Days at 90°F or more
- 31a normal year
- Days at 100°F or more
- 2a normal year
- Nights at 32°F or colder
- 224a normal year
- Days that stay below freezing
- 26high of 32°F or less
- Days with 0.01 inch of precipitation
- 88a normal year
The highest temperature in this station's record (since 1894) is 109°F, on July 29, 1934; the lowest is −38°F, on January 21, 1937.
The wettest calendar year on that record is 1970, with 34.94 in; the snowiest season is 1948–49, with 171.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00104442; records: ACIS (NOAA Regional Climate Centers), station USC00104442. Records use complete months only; a month missing more than three days is left out.
How sunny is Idaho City?
Over a year 81% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Idaho City, 4.6 kWh per square metre a day. July is the sunniest month (92%) and December the cloudiest (63%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 67% | 1.8 |
| February | 71% | 2.8 |
| March | 70% | 3.9 |
| April | 75% | 5.4 |
| May | 79% | 6.6 |
| June | 85% | 7.6 |
| July | 92% | 7.8 |
| August | 91% | 6.7 |
| September | 87% | 5.2 |
| October | 80% | 3.5 |
| November | 71% | 2.1 |
| December | 63% | 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 Idaho City need?
A normal year in Idaho City brings 7,892 heating degree days, 47% more than the median U.S. place (5,373), and 202 cooling degree days, 78% 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 1,586 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,259 | 0 |
| February | 1,030 | 0 |
| March | 933 | 0 |
| April | 697 | 0 |
| May | 453 | 2 |
| June | 233 | 17 |
| July | 59 | 100 |
| August | 77 | 75 |
| September | 276 | 8 |
| October | 636 | 0 |
| November | 977 | 0 |
| December | 1,263 | 0 |
| Year (annual) | 7,892 | 202 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00104442. 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.
How does Idaho City's climate compare?
Idaho City is warmer than 21 of the other 84 places with their own NOAA record in Idaho, and wetter than 57. Across the 7,247 U.S. stations with normals, its annual mean of 43.8°F is warmer than 15%.
In the Köppen classification computed from these normals, Idaho City 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.
Which places near Idaho City share this climate record?
Placerville has no NOAA station with 1991-2020 normals of its 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.
- Placerville, ID48 people · 9 mi NW
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 Idaho City's climate
What is the coldest month in Idaho City?
December, with a normal high of 35°F and a normal low of 14°F. The warmest is July (87°F by day, 46°F at night).
Does it snow in Idaho City?
Yes. NOAA publishes no 1991-2020 snowfall normal for Idaho City's NOAA station; the nearest record that keeps one, Garden Valley (19 miles away), records 69 inches of snow in a normal year.
What is the rainiest month in Idaho City?
December, with 3.53 in of precipitation in a normal year; the driest is July with 0.32 in.
What plant hardiness zone is Idaho City in?
The USDA's 2023 map puts Idaho City in zone 6b in ZIP code 83631, the nearest ZIP area.
How late can frost come in Idaho City?
In half of years the last 32°F night comes after June 17; in one year in ten it comes after July 4. Waiting until July 4 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Idaho climateThe statewide normals and every place in the state
- Arrowrock Dam, ID17 miles from this station, 51.0°F a year
- Garden Valley, ID19 miles from this station, 46.8°F a year
- Lowman, ID20 miles from this station, 44.3°F a year
- Boise Lucky Peak Dam, ID24 miles from this station, 52.8°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made