Climate and Average Weather Year Round in Glacier Bay National Park and Preserve United States

In Glacier Bay National Park and Preserve, the summers are cool, wet, and mostly cloudy and the winters are long, freezing, snowy, windy, and overcast. Over the course of the year, the temperature typically varies from 25°F to 64°F and is rarely below 6°F or above 71°F.

Based on the tourism score, the best time of year to visit Glacier Bay National Park and Preserve for warm-weather activities is from early July to mid August.

The warm season lasts for 3.6 months, from May 23 to September 12, with an average daily high temperature above 58°F. The hottest month of the year in Glacier Bay National Park and Preserve is July, with an average high of 63°F and low of 50°F.

The cold season lasts for 4.0 months, from November 9 to March 10, with an average daily high temperature below 40°F. The coldest month of the year in Glacier Bay National Park and Preserve is January, with an average low of 25°F and high of 35°F.

In Glacier Bay National Park and Preserve, 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 Glacier Bay National Park and Preserve begins around April 10 and lasts for 5.0 months, ending around September 11.

The clearest month of the year in Glacier Bay National Park and Preserve is August, during which on average the sky is clear, mostly clear, or partly cloudy 35% of the time.

The cloudier part of the year begins around September 11 and lasts for 7.0 months, ending around April 10.

The cloudiest month of the year in Glacier Bay National Park and Preserve is January, during which on average the sky is overcast or mostly cloudy 77% of the time.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Glacier Bay National Park and Preserve varies throughout the year.

The wetter season lasts 5.6 months, from August 23 to February 10, with a greater than 56% chance of a given day being a wet day. The month with the most wet days in Glacier Bay National Park and Preserve is October, with an average of 21.4 days with at least 0.04 inches of precipitation.

The drier season lasts 6.4 months, from February 10 to August 23. The month with the fewest wet days in Glacier Bay National Park and Preserve is June, with an average of 13.0 days with at least 0.04 inches of precipitation.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. The month with the most days of rain alone in Glacier Bay National Park and Preserve is October, with an average of 20.7 days. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 70% on October 9.

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. Glacier Bay National Park and Preserve experiences extreme seasonal variation in monthly rainfall.

Rain falls throughout the year in Glacier Bay National Park and Preserve. The month with the most rain in Glacier Bay National Park and Preserve is October, with an average rainfall of 13.4 inches.

The month with the least rain in Glacier Bay National Park and Preserve is June, with an average rainfall of 4.4 inches.

Snowfall

As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day of the year. Glacier Bay National Park and Preserve experiences extreme seasonal variation in monthly snowfall.

The snowy period of the year lasts for 5.8 months, from October 16 to April 9, with a sliding 31-day snowfall of at least 1.0 inches. The month with the most snow in Glacier Bay National Park and Preserve is January, with an average snowfall of 17.6 inches.

The snowless period of the year lasts for 6.2 months, from April 9 to October 16. The least snow falls around July 18, with an average total accumulation of 0.0 inches.

The length of the day in Glacier Bay National Park and Preserve varies extremely over the course of the year. In 2024, the shortest day is December 21, with 6 hours, 19 minutes of daylight; the longest day is June 20, with 18 hours, 21 minutes of daylight.

The earliest sunrise is at 3:59 AM on June 18, and the latest sunrise is 4 hours, 59 minutes later at 8:58 AM on December 27. The earliest sunset is at 3:14 PM on December 15, and the latest sunset is 7 hours, 6 minutes later at 10:20 PM on June 22.

Daylight saving time (DST) is observed in Glacier Bay National Park and Preserve during 2024, starting in the spring on March 10, lasting 7.8 months, and ending in the fall on November 3.

The figure below presents a compact representation of key lunar data for 2024. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases.

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 in Glacier Bay National Park and Preserve, 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.

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 in Glacier Bay National Park and Preserve experiences significant seasonal variation over the course of the year.

The windier part of the year lasts for 6.2 months, from September 24 to March 30, with average wind speeds of more than 8.5 miles per hour. The windiest month of the year in Glacier Bay National Park and Preserve is December, with an average hourly wind speed of 11.4 miles per hour.

The calmer time of year lasts for 5.8 months, from March 30 to September 24. The calmest month of the year in Glacier Bay National Park and Preserve is July, with an average hourly wind speed of 5.5 miles per hour.

The predominant average hourly wind direction in Glacier Bay National Park and Preserve varies throughout the year.

The wind is most often from the south for 4.3 months, from May 30 to October 7, with a peak percentage of 44% on July 16. The wind is most often from the east for 7.7 months, from October 7 to May 30, with a peak percentage of 52% on January 1.

Glacier Bay National Park and Preserve 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 3 to September 18, with an average temperature above 52°F. The month of the year in Glacier Bay National Park and Preserve with the warmest water is August, with an average temperature of 55°F.

The time of year with cooler water lasts for 4.7 months, from December 13 to May 2, with an average temperature below 44°F. The month of the year in Glacier Bay National Park and Preserve with the coolest water is March, with an average temperature of 41°F.

To characterize how pleasant the weather is in Glacier Bay National Park and Preserve 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 Glacier Bay National Park and Preserve 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 Glacier Bay National Park and Preserve for hot-weather activities is from mid June to early July, with a peak score in the last week of June.

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.

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 in Glacier Bay National Park and Preserve typically lasts for 4.7 months (142 days), from around May 12 to around October 1, rarely starting before April 22 or after May 29, and rarely ending before September 9 or after October 24.

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 in Glacier Bay National Park and Preserve should appear around June 7, only rarely appearing before May 23 or after June 23.

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 significant seasonal variation over the course of the year.

The brighter period of the year lasts for 3.1 months, from May 2 to August 5, with an average daily incident shortwave energy per square meter above 4.2 kWh. The brightest month of the year in Glacier Bay National Park and Preserve is June, with an average of 5.1 kWh.

The darker period of the year lasts for 4.3 months, from October 11 to February 20, with an average daily incident shortwave energy per square meter below 1.2 kWh. The darkest month of the year in Glacier Bay National Park and Preserve is December, with an average of 0.2 kWh.

For the purposes of this report, the geographical coordinates of Glacier Bay National Park and Preserve are 58.501 deg latitude, -137.001 deg longitude, and 0 ft elevation.

The topography within 2 miles of Glacier Bay National Park and Preserve is essentially flat, with a maximum elevation change of 0 feet and an average elevation above sea level of 0 feet. Within 10 miles is also essentially flat (0 feet). Within 50 miles is also essentially flat (0 feet).

The area within 2 miles of Glacier Bay National Park and Preserve is covered by snow and glaciers (80%) and bare soil (19%), within 10 miles by snow and glaciers (52%) and trees (15%), and within 50 miles by water (52%) and snow and glaciers (19%).