Thorne Bay, Alaska climate: Normal weather by month, frost dates and records
Thorne Bay's normal year runs from 28°F January nights to 66°F July afternoons, with 85.2 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 6.8°C, January lows of −2°C, July highs of 19°C, 2,164 mm of precipitation a year.
- NOAA stationThorne Bay
- Station IDUSC00509148
- Location55.69°N 132.52°W
- Elevation286 ft (87 m)
- Population474
On October 23, the normal high in Thorne Bay is 48°F and the normal low 36°F.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Thorne Bay.
- Jan 38° 28°
- Feb 40° 28°
- Mar 43° 30°
- Apr 50° 34°
- May 57° 40°
- Jun 63° 46°
- Jul 66° 51°
- Aug 65° 50°
- Sep 59° 45°
- Oct 51° 38°
- Nov 42° 32°
- Dec 38° 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 Thorne Bay each month?
July is the warmest month, with normal highs of 66°F; January the coldest, with normal lows of 28°F. The most precipitation falls in October (12.12 in), the least in May (3.51 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 38°F | 28°F | 33.2°F | 8.16 | – | <1 | 17 | 7 h 40 min |
| February | 40°F | 28°F | 33.9°F | 5.46 | – | <1 | 21 | 9 h 40 min |
| March | 43°F | 30°F | 36.2°F | 6.25 | – | <1 | 22 | 11 h 40 min |
| April | 50°F | 34°F | 41.9°F | 5.09 | – | <1 | 13 | 14 h 10 min |
| May | 57°F | 40°F | 48.6°F | 3.51 | – | <1 | 2 | 16 h 10 min |
| June | 63°F | 46°F | 54.4°F | 4.08 | – | <1 | <1 | 17 h 30 min |
| July | 66°F | 51°F | 58.1°F | 5.30 | – | <1 | <1 | 17 h |
| August | 65°F | 50°F | 57.8°F | 6.98 | – | <1 | <1 | 15 h 10 min |
| September | 59°F | 45°F | 52.1°F | 8.63 | – | <1 | <1 | 12 h 50 min |
| October | 51°F | 38°F | 44.3°F | 12.12 | – | <1 | 6 | 10 h 30 min |
| November | 42°F | 32°F | 37.0°F | 10.52 | – | <1 | 15 | 8 h 20 min |
| December | 38°F | 30°F | 33.7°F | 9.08 | – | <1 | 21 | 7 h |
| Year (annual) | 51°F | 38°F | 44.2°F | 85.18 | – | <1 | 118 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 3°C | −2°C | 0.7°C | 207 mm |
| February | 4°C | −2°C | 1.1°C | 139 mm |
| March | 6°C | −1°C | 2.3°C | 159 mm |
| April | 10°C | 1°C | 5.5°C | 129 mm |
| May | 14°C | 4°C | 9.2°C | 89 mm |
| June | 17°C | 8°C | 12.4°C | 104 mm |
| July | 19°C | 10°C | 14.5°C | 135 mm |
| August | 19°C | 10°C | 14.3°C | 177 mm |
| September | 15°C | 7°C | 11.2°C | 219 mm |
| October | 10°C | 3°C | 6.8°C | 308 mm |
| November | 5°C | 0°C | 2.8°C | 267 mm |
| December | 3°C | −1°C | 0.9°C | 231 mm |
NOAA publishes no 1991-2020 snowfall normal for this station, and no record within 25 miles keeps one, so snow is left out here rather than estimated.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00509148; 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 Thorne Bay?
Normal highs sit between 65°F and 85°F in July and August.
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 USC00509148.
When is the last frost in Thorne Bay?
In Thorne Bay, the last spring frost (32°F) comes after May 1 in half of years and after May 16 in one year in ten; the first autumn frost comes before October 13 in half of years and before October 1 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 11 year in 10 after May 16; 9 in 10 after April 17
- First autumn frost, half of years before
- October 131 year in 10 before October 1; 9 in 10 before October 28
NOAA puts the median frost-free season at 166 days, and the season without a hard freeze (28°F) at 202 days.
A hard freeze (28°F) comes after April 11 in half of springs and before October 30 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Thorne Bay in zone 7b in ZIP code 99919.
Frost dates for every NOAA station in Alaska · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00509148; 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 Thorne Bay?
In a normal year in Thorne Bay, a 90°F day is rare and 118 nights fall to 32°F or colder.
- Days at 90°F or more
- fewer than 1a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 118a normal year
- Days that stay below freezing
- 16high of 32°F or less
Source: NOAA NCEI 1991-2020 annual normals, station USC00509148.
How sunny is Thorne Bay?
Over a year 57% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Thorne Bay, 2.5 kWh per square metre a day. May is the sunniest month (61%) and January the cloudiest (46%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 46% | 0.5 |
| February | 56% | 1.2 |
| March | 56% | 2.3 |
| April | 60% | 3.6 |
| May | 61% | 4.6 |
| June | 57% | 4.6 |
| July | 55% | 4.2 |
| August | 59% | 3.7 |
| September | 56% | 2.5 |
| October | 52% | 1.4 |
| November | 48% | 0.6 |
| December | 47% | 0.3 |
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 Thorne Bay need?
A normal year in Thorne Bay brings 7,564 heating degree days, 41% more than the median U.S. place (5,373), and 11 cooling degree days, 99% fewer than the median (908). Ten months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 765 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 987 | 0 |
| February | 869 | 0 |
| March | 893 | 0 |
| April | 693 | 0 |
| May | 510 | 0 |
| June | 319 | 1 |
| July | 223 | 7 |
| August | 228 | 3 |
| September | 389 | 0 |
| October | 642 | 0 |
| November | 840 | 0 |
| December | 972 | 0 |
| Year (annual) | 7,564 | 11 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00509148. 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 Thorne Bay's climate compare?
Thorne Bay is warmer than 77 of the other 84 places with their own NOAA record in Alaska, and wetter than 61. Across the 7,247 U.S. stations with normals, its annual mean of 44.2°F is warmer than 16%.
In the Köppen classification computed from these normals, Thorne Bay is Cfb: temperate, 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.
Which places near Thorne Bay share this climate record?
3 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.
- Hollis, AK147 people · 14 mi SW
- Coffman Cove, AK128 people · 25 mi NW
- Kasaan, AK29 people · 10 mi SE
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 Thorne Bay's climate
What is the coldest month in Thorne Bay?
January, with a normal high of 38°F and a normal low of 28°F. The warmest is July (66°F by day, 51°F at night).
What is the rainiest month in Thorne Bay?
October, with 12.12 in of precipitation in a normal year; the driest is May with 3.51 in.
What plant hardiness zone is Thorne Bay in?
The USDA's 2023 map puts Thorne Bay in zone 7b in ZIP code 99919.
How late can frost come in Thorne Bay?
In half of years the last 32°F night comes after May 1; in one year in ten it comes after May 16. Waiting until May 16 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Alaska climateThe statewide normals and every place in the state
- Klawock, AK23 miles from this station, 45.2°F a year
- Craig, AK28 miles from this station, 44.9°F a year
- Ketchikan, AK39 miles from this station, 46.0°F a year
- Wrangell, AK54 miles from this station, 44.9°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made