Average Weather in Petersburg Alaska, United States
In Petersburg, the summers are cool, the winters are long and very cold, and it is wet and overcast year round. Over the course of the year, the temperature typically varies from 27°F to 64°F and is rarely below 11°F or above 71°F.
Based on the tourism score, the best time of year to visit Petersburg for warm-weather activities is from early July to mid August.
The warm season lasts for 3.5 months, from May 24 to September 9, with an average daily high temperature above 58°F. The hottest day of the year is July 31, with an average high of 64°F and low of 51°F.
The cold season lasts for 4.0 months, from November 12 to March 11, with an average daily high temperature below 41°F. The coldest day of the year is January 1, with an average low of 27°F and high of 35°F.
Average High and Low Temperature
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
In Petersburg, 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 in Petersburg begins around March 24 and lasts for 5.6 months, ending around September 13. On May 27, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 33% of the time, and overcast or mostly cloudy 67% of the time.
The cloudier part of the year begins around September 13 and lasts for 6.4 months, ending around March 24. On October 22, the cloudiest day of the year, the sky is overcast or mostly cloudy 81% of the time, and clear, mostly clear, or partly cloudy 19% of the time.
Cloud Cover Categories
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Petersburg varies significantly throughout the year.
The wetter season lasts 5.4 months, from August 26 to February 8, with a greater than 58% chance of a given day being a wet day. The chance of a wet day peaks at 75% on October 23.
The drier season lasts 6.6 months, from February 8 to August 26. The smallest chance of a wet day is 42% on May 28.
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 73% on October 20.
Daily Chance of Precipitation
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. Petersburg experiences extreme seasonal variation in monthly rainfall.
Rain falls throughout the year in Petersburg. The most rain falls during the 31 days centered around October 14, with an average total accumulation of 15.2 inches.
The least rain falls around June 8, with an average total accumulation of 4.4 inches.
Average Monthly Rainfall
We report snowfall in liquid-equivalent terms. The actual depth of new snowfall is typically between 5 and 10 times the liquid-equivalent amount, assuming the ground is frozen. Colder, drier snow tends to be on the higher end of that range and warmer, wetter snow on the lower end.
As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day of the year. Petersburg experiences significant seasonal variation in monthly liquid-equivalent snowfall.
The snowy period of the year lasts for 5.5 months, from October 21 to April 6, with a sliding 31-day liquid-equivalent snowfall of at least 0.1 inches. The most snow falls during the 31 days centered around January 15, with an average total liquid-equivalent accumulation of 1.5 inches.
The snowless period of the year lasts for 6.5 months, from April 6 to October 21. The least snow falls around July 21, with an average total liquid-equivalent accumulation of 0.0 inches.
Average Liquid-Equivalent Monthly Snowfall
The length of the day in Petersburg varies extremely over the course of the year. In 2018, the shortest day is December 21, with 6 hours, 45 minutes of daylight; the longest day is June 21, with 17 hours, 50 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 3:58 AM on June 18, and the latest sunrise is 4 hours, 31 minutes later at 8:29 AM on December 28. The earliest sunset is at 3:11 PM on December 14, and the latest sunset is 6 hours, 38 minutes later at 9:48 PM on June 23.
Daylight saving time (DST) is observed in Petersburg during 2018, starting in the spring on March 11, lasting 7.8 months, and ending in the fall on November 4.
Sunrise & Sunset with Twilight and Daylight Saving Time
The perceived humidity level in Petersburg, 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
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The average hourly wind speed in Petersburg experiences significant seasonal variation over the course of the year.
The windier part of the year lasts for 6.5 months, from October 2 to April 19, with average wind speeds of more than 6.7 miles per hour. The windiest day of the year is January 2, with an average hourly wind speed of 9.2 miles per hour.
The calmer time of year lasts for 5.5 months, from April 19 to October 2. The calmest day of the year is July 18, with an average hourly wind speed of 4.3 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Petersburg varies throughout the year.
The wind is most often from the south for 3.7 months, from June 15 to October 5, with a peak percentage of 41% on October 3. The wind is most often from the east for 8.3 months, from October 5 to June 15, with a peak percentage of 64% on January 1.
Petersburg 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 2.4 months, from July 5 to September 17, with an average temperature above 51°F. The day of the year with the warmest water is August 15, with an average temperature of 53°F.
The time of year with cooler water lasts for 4.5 months, from December 19 to May 1, with an average temperature below 44°F. The day of the year with the coolest water is March 11, with an average temperature of 41°F.
Average Water Temperature
Best Time of Year to Visit
To characterize how pleasant the weather is in Petersburg 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 Petersburg for general outdoor tourist activities is from early July to mid August, with a peak score in the last week of July.
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 Petersburg for hot-weather activities is from late July to early August.
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.
The growing season in Petersburg typically lasts for 5.9 months (180 days), from around April 25 to around October 22, rarely starting before April 9 or after May 14, and rarely ending before September 29 or after November 12.
Time Spent in Various Temperature Bands and the Growing Season
Based on growing degree days alone, the first spring blooms in Petersburg should appear around June 6, only rarely appearing before May 23 or after June 23.
Growing Degree Days
The average daily incident shortwave solar energy experiences significant seasonal variation over the course of the year.
The brighter period of the year lasts for 3.3 months, from April 27 to August 4, with an average daily incident shortwave energy per square meter above 4.1 kWh. The brightest day of the year is May 27, with an average of 5.1 kWh.
The darker period of the year lasts for 4.2 months, from October 13 to February 18, 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
For the purposes of this report, the geographical coordinates of Petersburg are 56.812 deg latitude, -132.956 deg longitude, and 82 ft elevation.
The topography within 2 miles of Petersburg contains large variations in elevation, with a maximum elevation change of 2,169 feet and an average elevation above sea level of 167 feet. Within 10 miles contains large variations in elevation (3,812 feet). Within 50 miles also contains extreme variations in elevation (10,026 feet).
The area within 2 miles of Petersburg is covered by trees (48%), water (39%), and sparse vegetation (12%), within 10 miles by trees (63%) and water (27%), and within 50 miles by trees (40%) and water (28%).
This report illustrates the typical weather in Petersburg, 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
There are 3 weather stations near enough to contribute to our estimation of the temperature and dew point in Petersburg.
For each station, the records are corrected for the elevation difference between that station and Petersburg according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.
The estimated value at Petersburg is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Petersburg and a given station.
The stations contributing to this reconstruction are: Petersburg James A. Johnson Airport (99%, 1.3 kilometers, southeast); Kake Airport (0.4%, 60 kilometers, west); and Port Alexander Seaplane Base (0.1%, 116 kilometers, southwest).
Time zones for aiports and weather stations are provided by AskGeo.com .