Port San Juan, AK Climate: Temperature & Rain by Month
Annual temperature and rainfall from NOAA NCEI's 1991–2020 normals →; comfort score computed by PlainClimate
30-year climate normals (1991-2020) from Port San Juan's primary NOAA station, PORT SAN JUAN.
The climate verdict for Port San Juan
Water is the standout signal in Port San Juan, Alaska: 137.9 inches of precipitation in a normal year. Against that wet profile, NOAA records an annual average of 41°F. At 28/100 (below average) the climate comfort score falls in the bottom third of the station-mapped U.S. score corpus, exceeding only 0% of scores.
- 41°F
- yearly average temperature, NOAA normal
- 28/100
- comfort score, above 0% of station-mapped location scores
- 137.9"
- yearly precipitation total
- 150 days
- frost-free growing season
Port San Juan: NOAA 1991-2020 normals describe a typical year, not a forecast. Method: /methodology.
Normals record plate
Sheet USC00507738 · Port San Juan, AK 41°F mean · 137.9" precip
TEMP-COOL · RANK-COOL · PHOTO-FINISH · PRCP-WET · SWING-NARROW · COMF-LOW · LOAD-HEAT · STN-1 · BOOK-FULL
- TEMP-COOL 41°F
- RANK-COOL #480
- PHOTO-FINISH ≈ Glacier Bay
- PRCP-WET 137.9"
- SWING-NARROW 26°F
- COMF-LOW 28/100
- LOAD-HEAT 8,759 HDD
- STN-1 USC00507738
- BOOK-FULL 6/6 fields
Nearest mean-temperature peer: Glacier Bay, AK (+ 0 °F mean)
Instrument codes from this station's NOAA 1991–2020 normals, mean temperature, corpus warmth rank, photo-finish peer station, precipitation band, seasonal swing, comfort composite, degree-day load, and field book, not a livability rating.
Mean-temperature neighbourhood
Nationwide NOAA normal poles and nearest peers, not a reprint of every AK station list.
- Port San Juan (this station) 41°F
- Hot Yakutat State, AK 41°F
- Near Glacier Bay, AK 41°F
- Near Kitoi Bay, AK 41°F
- Near Snettisham Pwr…, AK 41°F
Port San Juan sits in Alaska, the #1 coldest U.S. state at 33.5°F statewide annual average - see all 50 coldest states ranked by NOAA normals
Climate Living Index · Port San Juan
Port San Juan: 17/100 · grade F
Port San Juan publishes 4 of 6 Living Index dimensions (NOAA annual/seasonal normals · NOAA daily multivariate normals); 2 missing weights rescale to 100.
PlainClimate-derived for Port San Juan, not an official NOAA rating. Rankings still use Comfort Score 28/100 (separate formula). Breakpoints and limits.
| Dimension | Station value | Score |
|---|---|---|
| Normal heat + freeze calendar | 167 calendar days | 34/100 · F |
| Frost-free season | 150 days/year | 25/100 · F |
| Annual temperature balance | 40.9°F · 26.6° from 67.5°F | 7/100 · F |
| Precipitation balance | 137.9 in · 102.9 from 35 in | 0/100 · F |
Port San Juan · 2026-08-04 · NOAA NCEI Climate Normals · method · Comfort Score method.
Port San Juan is a continental Köppen climate: Dfc
Coldest-month mean 29.9°F and warmest-month mean 56.1°F place this station in continental, no dry season, cool summer climates (Dfc). Class Dfc is the Peel et al. (2007) label for this station's monthly mean temperature and precipitation normals: continental, specifically continental, no dry season, cool summer.
- Köppen code
- Dfc
- Group
- Continental
- Warmest month
- 56.1°F
- Coldest month
- 29.9°F
Source: official public datasets monthly normals (1991–2020) at the city’s primary station. This is a station classification, not a mapped regional consensus.
National standing · heating-led station
Where Port San Juan sits across the climate record
Three NOAA fields for Port San Juan's primary station, temperature, precipitation, and seasonal swing, are ranked against every station-mapped normal that carries the same field.
- Annual temperature
- Cooler than 93%
- Among 6,861 stations, Port San Juan sits in the cooler third of annual means.
- Annual precipitation
- Top 1% wettest
- Port San Juan's annual total ranks in the wetter third of 6,352 measured normals.
- Seasonal temperature swing
- Narrower than 94%
- Warmest-to-coldest month gap for Port San Juan is compact versus 6,861 complete station-years.
How Port San Juan compares across U.S. station-mapped locations
Port San Juan's comfort score vs. all station-mapped locations
PlainClimate composite comfort index (1–100), NOAA 1991–2020 normals
28 0th percentile score exceeds 0% of 6,189 station-mapped location scores
- 0–10: 0 station-mapped locations (0%). Below this entry.
- 10–20: 0 station-mapped locations (0%). Below this entry.
- 20–30: 96 station-mapped locations (2%). This entry sits in this band.
- 30–40: 280 station-mapped locations (5%). Above this entry.
- 40–50: 1,113 station-mapped locations (18%). Above this entry.
- 50–60: 1,329 station-mapped locations (21%). Above this entry.
- 60–70: 1,236 station-mapped locations (20%). Above this entry.
- 70–80: 650 station-mapped locations (11%). Above this entry.
- 80–90: 921 station-mapped locations (15%). Above this entry.
- 90–100: 564 station-mapped locations (9%). Above this entry.
Source NOAA U.S. Climate Normals, PlainClimate comfort index · 1991–2020
Monthly Temperatures
Average daily high and low temperatures by month
| Month | Avg High | Avg Low | Mean | Precip | Freeze Days | 90°F+ Days |
|---|---|---|---|---|---|---|
| January | 34°F (1°C) | 26°F (-3°C) | 30°F (-1°C) | 12.3" | 23.2 | 0.0 |
| February | 35°F (2°C) | 26°F (-3°C) | 31°F (-1°C) | 11.6" | 20.7 | 0.0 |
| March | 36°F (2°C) | 26°F (-3°C) | 31°F (0°C) | 9.6" | 24.3 | 0.0 |
| April | 43°F (6°C) | 32°F (0°C) | 37°F (3°C) | 10.3" | 14.7 | 0.0 |
| May | 52°F (11°C) | 37°F (3°C) | 45°F (7°C) | 8.1" | 3.3 | 0.0 |
| June | 59°F (15°C) | 44°F (7°C) | 52°F (11°C) | 4.5" | 0.1 | 0.0 |
| July | 63°F (17°C) | 50°F (10°C) | 56°F (13°C) | 5.3" | 0.0 | 0.0 |
| August | 61°F (16°C) | 49°F (10°C) | 55°F (13°C) | 9.8" | 0.0 | 0.0 |
| September | 54°F (12°C) | 44°F (6°C) | 49°F (9°C) | 17.4" | 0.6 | 0.0 |
| October | 45°F (7°C) | 36°F (2°C) | 41°F (5°C) | 17.3" | 7.9 | 0.0 |
| November | 38°F (3°C) | 30°F (-1°C) | 34°F (1°C) | 15.9" | 18.7 | 0.0 |
| December | 36°F (2°C) | 28°F (-2°C) | 32°F (0°C) | 15.8" | 22.1 | 0.0 |
The year, day by day
Summer here tops out rather than builds: the warmest normal high is 63°F around July 25, short of 90°F on every date, while 167 dates carry a normal low at or below freezing, the coldest 26°F near January 11.
The freezing stretch
The normal low stays at or below 32°F into April 16, then returns to freezing around November 2, covering 167 dates in all.
Derived from the normal daily minimum. This is a different measure from the 50%-probability frost dates shown elsewhere on this page, which come from NOAA’s frost product.
Where the wet dates fall
The likeliest wet date is December 12, when 70% of years recorded at least a hundredth of an inch. The driest is June 24 at 44%. Summed across the calendar, that is about 216 wet dates a year.
The widest day
May 31 carries the biggest normal gap between afternoon and dawn, 16°F between the normal high and the normal low.
Look up any date
Any date's 1991–2020 normal for Port San Juan.
Where Port San Juan Stands Nationally
This is one of the wettest normals climates ranked: about 138 inches of precipitation in a normal year, a total fewer than one station in ten surpasses.
Among the steadiest day-night climates ranked: even the widest normal daily swing holds to roughly 16°F.
Port San Juan earns 2 nationally notable standings (outer quintiles) against 6,860 NOAA 1991–2020 normals stations; only those extremes render.
Monthly Precipitation
Average monthly rainfall
20.0 days with precipitation
18.0 days with precipitation
17.3 days with precipitation
17.7 days with precipitation
15.7 days with precipitation
13.7 days with precipitation
15.2 days with precipitation
16.3 days with precipitation
19.9 days with precipitation
20.7 days with precipitation
19.1 days with precipitation
22.0 days with precipitation
Port San Juan spreads its precipitation across the year
Neither half of the year dominates here: June through August take 14% of the annual total and December through February 29%, with neither reaching the 35% that would mark a distinct wet season. Port San Juan has no dry season to plan around, though it does carry an unusually narrow 26.2°F seasonal spread.
The gap between the wettest and driest month still matters: September averages 17.4" and June 4.5". The three wettest months together take 37% of the year, against the 25% a perfectly flat distribution would give them.
Shares are computed from this station's own 1991-2020 monthly precipitation normals. "Spread across the year" means neither the June-August nor the December-February share reaches 35%; it describes an average year, not the variability of any single one.
When it rains in Port San Juan, it arrives in quantity
137.9" of precipitation falls across only about 216 wet days here, averaging 0.64 inches each. Fewer days carry more water: the year's total is delivered in comparatively heavy events rather than persistent damp.
- Days with measurable precipitation
- about 216 a year, 59% of all days
- Average depth per wet day
- 0.64 inches
- Most wet days
- December, about 22
- Fewest wet days
- June, about 14
A wet day is one recording at least 0.01 inches. These are 1991-2020 normals: they describe an average year, and a per-day average is not a forecast of any individual storm.
Frost Dates & Growing Season
First Fall Freeze
October 7
50% probability date
Last Spring Freeze
May 10
50% probability date
Growing Season
150 days
Heating & Cooling Degree Days
Annual totals indicate energy demand for heating and cooling
Heating Degree Days
8,759
Higher = more heating needed
Cooling Degree Days
1
Higher = more cooling needed
Warmest Month
July
Coldest Month
January
Nationwide similar cities
Other rankable U.S. places outside AK closest to Port San Juan on two NOAA annual-normal axes (mean temperature and annual precipitation). Chip rows use distinct link sets.
Closest by average temperature
Nearest out-of-state peers by annual mean temperature (41°F here).
- Danforth, ME 41°F · 0.0°F off
- Fessenden, ND 41°F · 0.0°F off
- Munising, MI 41°F · 0.0°F off
- Ottertail, MN 41°F · 0.0°F off
Closest by annual precipitation
Nearest out-of-state peers by annual precipitation (137.9" here), excluding temperature-peer places.
- Hilo, HI 120.4" · 17.5" off
- Forks, WA 119.9" · 17.9" off
- Cougar, WA 115.3" · 22.6" off
- Naselle, WA 112.2" · 25.7" off
Data-derived climate profile
How Port San Juan's climate pattern fits together
heating led · wet · low swing
Heating is the larger measured load in Port San Juan, at 8,759 degree days versus 1 for cooling. Unlike a strongly continental record, however, its 26.2°F month-to-month range is compact; persistent cool-season demand matters more than a dramatic summer-to-winter reversal.
Port San Juan's frost-free season lasts about 150 days, a middle-length window whose endpoints matter more than the annual average. It describes freeze probability, not year-specific planting conditions.
Port San Juan's 26.2°F seasonal spread is compact even though precipitation is abundant. July and January mark the typical warm and cold ends of the calendar. The annual average is 41°F. Temperature is relatively steady; the monthly rows show how rain and snow observations vary across the calendar.
Alongside its heating load, Port San Juan carries 137.9 inches of precipitation in a normal year, inside PlainClimate's wet range. Snowfall is not added to the interpretation because its annual value is missing. That distinction matters because a wet annual total can arrive as rain, snow, or a mixture at different times.
These labels group NOAA 1991-2020 normals from Port San Juan's primary station, so the winter figures are a thirty-year average and not a floor: a single hard season can run well below them. Treat each band as a descriptive range for Port San Juan, not an official NOAA class or a year-ahead forecast.
Questions about Port San Juan's climate
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Data Sources
Data source: NOAA U.S. Climate Normals v1.0.1 (1991-2020). All figures on this page are from Port San Juan's primary station: PORT SAN JUAN (USC00507738). For informational purposes only.
Place identity: U.S. Census Bureau 2024 Gazetteer places. The conservative exact name-and-state crosswalk finds no Census place match, so PlainClimate treats this as a station-mapped location and does not claim it is a municipality. No exact Gazetteer row for Port San Juan; facility counts that depend on place identity are therefore an upper bound, not a municipal census.
On this page every temperature, precipitation, and derived score for Port San Juan comes from its primary NOAA station record. No figure on this page is typed in by an editor - each value is rendered from NOAA 1991-2020 U.S. Climate Normals. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 1991–2020 normals.