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Average Weather at Port Alexander Seaplane Base Alaska, United States

At Port Alexander Seaplane Base, the summers are cool and mostly cloudy; the winters are long, very cold, extremely windy, and overcast; and it is wet year round. Over the course of the year, the temperature typically varies from 35°F to 59°F and is rarely below 24°F or above 67°F.

Climate Summary

very coldcoldcoolcoldvery coldJanFebMarAprMayJunJulAugSepOctNovDec41%41%23%23%overcastclearprecipitation: 12.9 inprecipitation: 12.9 in3.7 in3.7 inmuggy: 0%muggy: 0%drydrytourism score: 3.1tourism score: 3.10.00.0
Click on each chart for more information.

Based on the tourism score, the best time of year to visit Port Alexander Seaplane Base for warm-weather activities is from late July to late August.

Temperature

The warm season lasts for 3.5 months, from May 27 to September 11, with an average daily high temperature above 56°F. The hottest day of the year is August 4, with an average high of 59°F and low of 51°F.

The cool season lasts for 4.6 months, from November 11 to March 31, with an average daily high temperature below 47°F. The coldest day of the year is February 23, with an average low of 35°F and high of 44°F.

Average High and Low Temperature

The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.

The figure below shows you a compact characterization of the entire year of hourly average temperatures. The horizontal axis is the day of the year, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

Average Hourly Temperature

Average Hourly Temperature at Port Alexander Seaplane BaseJanFebMarAprMayJunJulAugSepOctNovDec12 AM4 AM8 AM12 PM4 PM8 PM12 AMvery coldvery coldcoldcool
The average hourly temperature, color coded into bands: frigid < 15°F < freezing < 32°F < very cold < 45°F < cold < 55°F < cool < 65°F < comfortable < 75°F < warm < 85°F < hot < 95°F < sweltering. The shaded overlays indicate night and civil twilight.

Portree, United Kingdom (4,084 miles away) is the far-away foreign place with temperatures most similar to Port Alexander Seaplane Base (view comparison).

Clouds

At Port Alexander Seaplane Base, the average percentage of the sky covered by clouds experiences mild seasonal variation over the course of the year.

The clearer part of the year at Port Alexander Seaplane Base begins around April 21 and lasts for 5.1 months, ending around September 25. On August 12, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 41% of the time, and overcast or mostly cloudy 59% of the time.

The cloudier part of the year begins around September 25 and lasts for 6.9 months, ending around April 21. On January 24, the cloudiest day of the year, the sky is overcast or mostly cloudy 77% of the time, and clear, mostly clear, or partly cloudy 23% of the time.

Cloud Cover Categories

Cloud Cover Categories at Port Alexander Seaplane BaseclearercloudiercloudierJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%Aug 1241%Aug 1241%Jan 2423%Jan 2423%Apr 2132%Apr 2132%Sep 2532%Sep 2532%clearmostly clearpartly cloudymostly cloudyovercast
The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds: clear < 20% < mostly clear < 40% < partly cloudy < 60% < mostly cloudy < 80% < overcast.

Precipitation

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days at Port Alexander Seaplane Base varies significantly throughout the year.

The wetter season lasts 7.0 months, from August 27 to March 26, with a greater than 54% chance of a given day being a wet day. The chance of a wet day peaks at 73% on October 31.

The drier season lasts 5.0 months, from March 26 to August 27. The smallest chance of a wet day is 35% on June 21.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 72% on October 31.

Daily Chance of Precipitation

Daily Chance of Precipitation at Port Alexander Seaplane BasewetwetdryJanFebMarAprMayJunJulAugSepOctNovDec0%10%20%30%40%50%60%70%80%90%100%Oct 3173%Oct 3173%Jun 2135%Jun 2135%Jan 164%Jan 164%Aug 2754%Aug 2754%Mar 2654%Mar 2654%rainmixed
The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).

Rainfall

To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. Port Alexander Seaplane Base experiences extreme seasonal variation in monthly rainfall.

Rain falls throughout the year at Port Alexander Seaplane Base. The most rain falls during the 31 days centered around October 16, with an average total accumulation of 12.9 inches.

The least rain falls around June 21, with an average total accumulation of 3.7 inches.

Average Monthly Rainfall

Average Monthly Rainfall at Port Alexander Seaplane BaseJanFebMarAprMayJunJulAugSepOctNovDec0 in5 in10 in15 in20 inOct 1612.9 inOct 1612.9 inJun 213.7 inJun 213.7 in
The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average liquid-equivalent snowfall.

Snowfall

The sliding 31-day liquid-equivalent quantity of snowfall at Port Alexander Seaplane Base does not vary significantly over the course of the year, staying within 0.1 inches of 0.1 inches throughout.

Average Liquid-Equivalent Monthly Snowfall

Average Liquid-Equivalent Monthly Snowfall at Port Alexander Seaplane BasesnowJanFebMarAprMayJunJulAugSepOctNovDec0 in2 in4 in6 in8 in10 in12 in14 inJan 270.2 inJan 270.2 inAug 20.0 inAug 20.0 inDec 300.1 inDec 300.1 inFeb 250.1 inFeb 250.1 in
The average liquid-equivalent snowfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average rainfall.

Sun

The length of the day at Port Alexander Seaplane Base varies extremely over the course of the year. In 2017, the shortest day is December 21, with 6 hours, 53 minutes of daylight; the longest day is June 20, with 17 hours, 41 minutes of daylight.

Hours of Daylight and Twilight

Hours of Daylight and Twilight at Port Alexander Seaplane BaseJanFebMarAprMayJunJulAugSepOctNovDec0 hr24 hr4 hr20 hr8 hr16 hr12 hr12 hr16 hr8 hr20 hr4 hr24 hr0 hr12 hr, 9 minMar 2012 hr, 9 minMar 2017 hr, 41 minJun 2017 hr, 41 minJun 2012 hr, 12 minSep 2212 hr, 12 minSep 226 hr, 54 minDec 216 hr, 54 minDec 21nightnightday
The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

The earliest sunrise is at 4:09 AM on June 18, and the latest sunrise is 4 hours, 22 minutes later at 8:31 AM on December 28. The earliest sunset is at 3:21 PM on December 14, and the latest sunset is 6 hours, 29 minutes later at 9:51 PM on June 23.

Daylight saving time (DST) is observed at Port Alexander Seaplane Base during 2017, starting in the spring on March 12, lasting 7.8 months, and ending in the fall on November 5.

Sunrise & Sunset with Twilight and Daylight Saving Time

Sunrise & Sunset with Twilight and Daylight Saving Time at Port Alexander Seaplane BaseJanFebMarAprMayJunJulAugSepOctNovDec12 AM2 AM4 AM6 AM8 AM10 AM12 PM2 PM4 PM6 PM8 PM10 PM12 AMJun 184:09 AMJun 184:09 AM9:51 PMJun 239:51 PMJun 23Dec 143:21 PMDec 143:21 PM8:31 AMDec 288:31 AMDec 28Mar 12DSTMar 12DSTDSTNov 5DSTNov 5daynightnightnightnightSolarMidnightSolarMidnightSolarNoonSunriseSunset
The solar day over the course of the year 2017. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray. The transitions to and from daylight saving time are indicated by the 'DST' labels.

Humidity

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

The perceived humidity level at Port Alexander Seaplane Base, as measured by the percentage of time in which the humidity comfort level is muggy, oppressive, or miserable, does not vary significantly over the course of the year, remaining a virtually constant 0% throughout.

Humidity Comfort Levels

Humidity Comfort Levels at Port Alexander Seaplane BaseJanFebMarAprMayJunJulAugSepOctNovDec0%10%20%30%40%50%60%70%80%90%100%Jul 30%Jul 30%drydrycomfortablecomfortable
The percentage of time spent at various humidity comfort levels, categorized by dew point: dry < 55°F < comfortable < 60°F < humid < 65°F < muggy < 70°F < oppressive < 75°F < miserable.

Wind

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed at Port Alexander Seaplane Base experiences extreme seasonal variation over the course of the year.

The windier part of the year lasts for 6.8 months, from September 25 to April 19, with average wind speeds of more than 13.7 miles per hour. The windiest day of the year is December 6, with an average hourly wind speed of 17.7 miles per hour.

The calmer time of year lasts for 5.2 months, from April 19 to September 25. The calmest day of the year is July 18, with an average hourly wind speed of 9.6 miles per hour.

Average Wind Speed

Average Wind Speed at Port Alexander Seaplane BasewindywindyJanFebMarAprMayJunJulAugSepOctNovDec0 mph5 mph10 mph15 mph20 mph25 mphDec 617.7 mphDec 617.7 mphJul 189.6 mphJul 189.6 mphSep 2513.7 mphSep 2513.7 mphApr 1913.7 mphApr 1913.7 mph
The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.

The predominant average hourly wind direction at Port Alexander Seaplane Base varies throughout the year.

The wind is most often from the south for 2.5 months, from March 31 to June 14 and for 4.1 months, from August 13 to December 17, with a peak percentage of 43% on October 8. The wind is most often from the west for 2.0 months, from June 14 to August 13, with a peak percentage of 43% on July 16. The wind is most often from the east for 3.5 months, from December 17 to March 31, with a peak percentage of 39% on January 1.

Wind Direction

Wind Direction at Port Alexander Seaplane BaseESWSEJanFebMarAprMayJunJulAugSepOctNovDec0%100%20%80%40%60%60%40%80%20%100%0%westsoutheastnorth
The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions (north, east, south, and west), excluding hours in which the mean wind speed is less than 1 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Water Temperature

Port Alexander Seaplane Base is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.

The average water temperature experiences some seasonal variation over the course of the year.

The time of year with warmer water lasts for 2.5 months, from July 8 to September 23, with an average temperature above 52°F. The day of the year with the warmest water is August 15, with an average temperature of 54°F.

The time of year with cooler water lasts for 4.5 months, from December 21 to May 5, with an average temperature below 45°F. The day of the year with the coolest water is March 11, with an average temperature of 42°F.

Average Water Temperature

Average Water Temperature at Port Alexander Seaplane BasewarmcoolJanFebMarAprMayJunJulAugSepOctNovDec38°F40°F42°F44°F46°F48°F50°F52°F54°F56°F58°FAug 1554°FAug 1554°F42°FMar 1142°FMar 11Jul 852°FJul 852°FSep 2352°FSep 2352°FDec 2145°FDec 2145°FMay 545°FMay 545°F
The daily average water temperature (purple line), with 25th to 75th and 10th to 90th percentile bands.

Best Time of Year to Visit

To characterize how pleasant the weather is at Port Alexander Seaplane Base throughout the year, we compute two travel scores.

The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best time of year to visit Port Alexander Seaplane Base for general outdoor tourist activities is from late July to late August, with a peak score in the first week of August.

Tourism Score

Tourism Score at Port Alexander Seaplane BaseJanFebMarAprMayJunJulAugSepOctNovDec02468103.13.10.00.0 precipitationprecipitationcloudscloudstemperaturetemperature
The tourism score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).

The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit Port Alexander Seaplane Base for hot-weather activities is from late July to mid August.

Beach/Pool Score

Beach/Pool Score at Port Alexander Seaplane BaseJanFebMarAprMayJunJulAugSepOctNovDec02468100.10.10.00.0precipitationprecipitationcloudscloudstemperaturetemperature
The beach/pool score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).

Methodology

For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.

Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.

Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.

Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.

Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.

Growing Season

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

The growing season at Port Alexander Seaplane Base typically lasts for 7.3 months (224 days), from around March 23 to around November 2, rarely starting before February 20 or after May 3, and rarely ending before October 5 or after December 11.

Time Spent in Various Temperature Bands and the Growing Season

Time Spent in Various Temperature Bands and the Growing Season at Port Alexander Seaplane Basegrowing seasonJanFebMarAprMayJunJulAugSepOctNovDec0%100%10%90%20%80%30%70%40%60%50%50%60%40%70%30%80%20%90%10%100%0%50%Mar 2350%Mar 2350%Nov 250%Nov 290%May 390%May 390%Oct 590%Oct 510%Feb 2010%Feb 2010%Dec 1110%Dec 113%Jan 93%Jan 9Jul 24100%Jul 24100%very coldcoldcool
The percentage of time spent in various temperature bands: frigid < 15°F < freezing < 32°F < very cold < 45°F < cold < 55°F < cool < 65°F < comfortable < 75°F < warm < 85°F < hot < 95°F < sweltering. The black line is the percentage chance that a given day is within the growing season.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

Based on growing degree days alone, the first spring blooms at Port Alexander Seaplane Base should appear around June 11, only rarely appearing before May 21 or after July 20.

Growing Degree Days

Growing Degree Days at Port Alexander Seaplane BaseJanFebMarAprMayJunJulAugSepOctNovDec0°F100°F200°F300°F400°F500°F600°F700°FJun 1190°FJun 1190°FDec 31504°FDec 31504°F
The average growing degree days accumulated over the course of the year, with 25th to 75th and 10th to 90th percentile bands.

Solar Energy

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy experiences extreme seasonal variation over the course of the year.

The brighter period of the year lasts for 3.2 months, from May 7 to August 13, with an average daily incident shortwave energy per square meter above 4.4 kWh. The brightest day of the year is June 20, with an average of 5.5 kWh.

The darker period of the year lasts for 4.2 months, from October 15 to February 23, with an average daily incident shortwave energy per square meter below 1.3 kWh. The darkest day of the year is December 20, with an average of 0.3 kWh.

Average Daily Incident Shortwave Solar Energy

Average Daily Incident Shortwave Solar Energy at Port Alexander Seaplane BasebrightdarkdarkJanFebMarAprMayJunJulAugSepOctNovDec0 kWh1 kWh2 kWh3 kWh4 kWh5 kWh6 kWh7 kWh8 kWhJun 205.5 kWhJun 205.5 kWhDec 200.3 kWhDec 200.3 kWhMay 74.4 kWhMay 74.4 kWhAug 134.4 kWhAug 134.4 kWhOct 151.3 kWhOct 151.3 kWhFeb 231.3 kWhFeb 231.3 kWh
The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

Data Sources

This report illustrates the typical weather at Port Alexander Seaplane Base, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.

Temperature and Dew Point

Port Alexander Seaplane Base has a weather station that reported reliably enough during the analysis period that we have included it in our network. When available, historical temperature and dew point measurements are taken directly from this weather station. These records are obtained from NOAA's Integrated Surface Hourly data set, falling back on ICAO METAR records as required.

In the case of missing or erroneous measurements from this station, we fall back on records from nearby stations, adjusted according to typical seasonal and diurnal intra-station differences. For a given day of the year and hour of the day, the fallback station is selected to minimize the prediction error over the years for which there are measurements for both stations.

The stations on which we may fall back are Kake Airport, Klawock Airport, Petersburg James A. Johnson Airport, Hydaburg Seaplane Base, Wrangell Airport, Ketchikan International Airport, Metlakatla Seaplane Base, and Annette Island Airport.

Other Data

All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Tables of the Sun, Moon and Planets , by Jean Meeus.

All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.

Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.

Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.

Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .

Time zones for aiports and weather stations are provided by AskGeo.com .

Maps are © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.

Disclaimer

The information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site.

We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands.

We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader.