Porthill (1 mi SW), Idaho climate: Climate normals at a NOAA weather station
Porthill (1 mi SW)'s normal year runs from 21°F January nights to 86°F July afternoons, with 21.5 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 8.5°C, January lows of −6°C, July highs of 30°C, 546 mm of precipitation a year.
- NOAA stationPorthill (1 mi SW)
- Station IDUSC00107264
- Location48.99°N 116.50°W
- Elevation1,799 ft (548 m)
On October 24, the normal high in Porthill (1 mi SW) is 54°F and the normal low 31°F, and the chance of measurable rain or snow is 31%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Porthill (1 mi SW).
- Jan 36° 21°
- Feb 40° 22°
- Mar 50° 28°
- Apr 60° 34°
- May 71° 42°
- Jun 76° 48°
- Jul 86° 52°
- Aug 86° 50°
- Sep 74° 42°
- Oct 58° 33°
- Nov 44° 27°
- Dec 36° 21°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like at Porthill (1 mi SW) each month?
July is the warmest month, with normal highs of 86°F; January the coldest, with normal lows of 21°F. The most precipitation falls in December (2.45 in), the least in August (0.82 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 36°F | 21°F | 28.2°F | 2.16 | 11 | <1 | 29 | 8 h 40 min |
| February | 40°F | 22°F | 31.1°F | 1.70 | 9 | <1 | 26 | 10 h 10 min |
| March | 50°F | 28°F | 38.8°F | 1.91 | 10 | <1 | 25 | 11 h 50 min |
| April | 60°F | 34°F | 47.1°F | 1.65 | 10 | <1 | 12 | 13 h 40 min |
| May | 71°F | 42°F | 56.4°F | 2.19 | 10 | <1 | 2 | 15 h 10 min |
| June | 76°F | 48°F | 61.9°F | 2.10 | 11 | 1 | <1 | 16 h 10 min |
| July | 86°F | 52°F | 68.8°F | 1.24 | 7 | 9 | <1 | 15 h 50 min |
| August | 86°F | 50°F | 67.6°F | 0.82 | 4 | 8 | <1 | 14 h 30 min |
| September | 74°F | 42°F | 58.1°F | 1.06 | 6 | 1 | 2 | 12 h 40 min |
| October | 58°F | 33°F | 45.7°F | 1.80 | 9 | <1 | 15 | 10 h 50 min |
| November | 44°F | 27°F | 35.7°F | 2.41 | 12 | <1 | 22 | 9 h 10 min |
| December | 36°F | 21°F | 28.4°F | 2.45 | 12 | <1 | 28 | 8 h 20 min |
| Year (annual) | 60°F | 35°F | 47.3°F | 21.49 | 109 | 20 | 162 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 2°C | −6°C | −2.1°C | 55 mm |
| February | 5°C | −6°C | −0.5°C | 43 mm |
| March | 10°C | −2°C | 3.8°C | 49 mm |
| April | 16°C | 1°C | 8.4°C | 42 mm |
| May | 22°C | 6°C | 13.6°C | 56 mm |
| June | 24°C | 9°C | 16.6°C | 53 mm |
| July | 30°C | 11°C | 20.4°C | 31 mm |
| August | 30°C | 10°C | 19.8°C | 21 mm |
| September | 23°C | 6°C | 14.5°C | 27 mm |
| October | 15°C | 1°C | 7.6°C | 46 mm |
| November | 7°C | −3°C | 2.1°C | 61 mm |
| December | 2°C | −6°C | −2.0°C | 62 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Bonners Ferry (23 miles away), gets 54 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00107264; 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.
Which months are mildest at Porthill (1 mi SW)?
Normal highs sit between 65°F and 85°F in May, June and September. Of those, September has the fewest days with rain (6).
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 USC00107264.
When is the last frost at Porthill (1 mi SW)?
In Porthill (1 mi SW), the last spring frost (32°F) comes after May 4 in half of years and after May 28 in one year in ten; the first autumn frost comes before September 30 in half of years and before September 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
- May 41 year in 10 after May 28; 9 in 10 after April 20
- First autumn frost, half of years before
- September 301 year in 10 before September 10; 9 in 10 before October 14
NOAA puts the median frost-free season at 145 days, and the season without a hard freeze (28°F) at 175 days.
A hard freeze (28°F) comes after April 16 in half of springs and before October 11 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Porthill (1 mi SW) in zone 6a in ZIP code 83805, the nearest ZIP area. By the map's own method, the average of each year's coldest night over 1991-2020, the station is in zone 6b: the coldest night of a typical year reaches −5°F (18 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 USC00107264; 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 at Porthill (1 mi SW)?
In a normal year in Porthill (1 mi SW), 20 days a year reach 90°F (1 of them 100°F or more), 162 nights fall to 32°F or colder and 109 days bring measurable precipitation.
- Days at 90°F or more
- 20a normal year
- Days at 100°F or more
- 1a normal year
- Nights at 32°F or colder
- 162a normal year
- Days that stay below freezing
- 35high of 32°F or less
- Days with 0.01 inch of precipitation
- 109a normal year
The highest temperature in this station's record (since 1893) is 108°F, on July 1, 2021; the lowest is −37°F, on December 30, 1968.
The wettest calendar year on that record is 1974, with 26.06 in; the snowiest season is 1949–50, with 152.0 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00107264; records: ACIS (NOAA Regional Climate Centers), station USC00107264. Records use complete months only; a month missing more than three days is left out.
How sunny is it at Porthill (1 mi SW)?
Over a year 71% of the sunlight that would reach the ground under clear skies gets through the clouds at Porthill (1 mi SW), 3.6 kWh per square metre a day. July is the sunniest month (87%) and December the cloudiest (48%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 50% | 1.0 |
| February | 60% | 1.9 |
| March | 59% | 2.9 |
| April | 65% | 4.4 |
| May | 71% | 5.7 |
| June | 70% | 6.0 |
| July | 87% | 7.2 |
| August | 86% | 5.9 |
| September | 79% | 4.2 |
| October | 68% | 2.4 |
| November | 53% | 1.2 |
| December | 48% | 0.8 |
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 many heating and cooling degree days does Porthill (1 mi SW) record?
A normal year at Porthill (1 mi SW) brings 6,757 heating degree days, 26% more than the median U.S. place (5,373), and 333 cooling degree days, 63% 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 2,018 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,141 | 0 |
| February | 951 | 0 |
| March | 811 | 0 |
| April | 537 | 0 |
| May | 278 | 10 |
| June | 132 | 39 |
| July | 34 | 151 |
| August | 42 | 121 |
| September | 220 | 13 |
| October | 600 | 0 |
| November | 878 | 0 |
| December | 1,136 | 0 |
| Year (annual) | 6,757 | 333 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00107264. 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.
Have recent years at Porthill (1 mi SW) been warmer than normal?
Over 101 complete years from 1890 to 2020, the station's annual mean temperature rose at a fitted 1.5°F per century (+0.08°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Porthill (1 mi SW)'s climate compare?
Porthill (1 mi SW) is warmer than 52 of the 85 places with their own NOAA record in Idaho, and wetter than 59. Across the 7,247 U.S. stations with normals, its annual mean of 47.3°F is warmer than 29%.
In the Köppen classification computed from these normals, Porthill (1 mi SW) is Dfb: continental, no dry season, 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 Porthill (1 mi SW)'s climate
What is the coldest month at Porthill (1 mi SW)?
January, with a normal high of 36°F and a normal low of 21°F. The warmest is July (86°F by day, 52°F at night).
Does it snow at Porthill (1 mi SW)?
Yes. NOAA publishes no 1991-2020 snowfall normal for the station; the nearest record that keeps one, Bonners Ferry (23 miles away), records 54 inches of snow in a normal year.
What is the rainiest month at Porthill (1 mi SW)?
December, with 2.45 in of precipitation in a normal year; the driest is August with 0.82 in.
What plant hardiness zone is Porthill (1 mi SW) in?
The USDA's 2023 map puts Porthill (1 mi SW) in zone 6a in ZIP code 83805, the nearest ZIP area. By the same method at the station, the coldest night of a typical year reaches −5°F (18 years, 1991-2020): zone 6b.
How late can frost come at Porthill (1 mi SW)?
In half of years the last 32°F night comes after May 4; in one year in ten it comes after May 28. Waiting until May 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
- Bonners Ferry, ID22 miles from this station, 47.6°F a year
- Boundary Dam, WA39 miles from this station, 46.0°F a year
- Yaak, MT40 miles from this station, 41.0°F a year
- Troy, MT45 miles from this station, 46.8°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made