Anchorage, Alaska (Dena'ina: Dgheyay Kaq'; Dgheyaytnu) has a subarctic climate with the code Dsc according to the Köppen climate classification because its summers are short and cool. The weather in Anchorage is hard to predict from day to day. Some winters have several feet of snow and very cold temperatures, while summers are usually mild but cooler than summers in the contiguous United States and interior Alaska. Anchorage’s high latitude causes summer days to be very long and winter days to be very short. The longest day of sunlight lasts 19 hours and 21 minutes, and the shortest day has only 5 hours and 28 minutes of daylight. Anchorage is often cloudy in the winter, which reduces the amount of sunlight that reaches the area.
Temperature
In summer, average daytime temperatures range from about 55 to 78 °F (13 to 26 °C). In winter, average daytime temperatures range from about 5 to 30 °F (−15 to −1 °C). Anchorage has a growing season without frost that lasts about 100 days on average. At Ted Stevens Anchorage International Airport (PANC), the average January temperatures are 11 °F (−11.7 °C) for lows and 23 °F (−5.0 °C) for highs. Winter snowfall averages 75.59 inches (1.92 meters). At the Campbell Airstrip, another weather station records colder nighttime temperatures in both summer and winter.
In July, average temperatures are 52 °F (11.1 °C) for lows and 66 °F (18.9 °C) for highs. The highest temperature ever recorded was 90 °F (32.2 °C) on July 4, 2019.
Precipitation
From 2000 to 2022, the average yearly rainfall in Anchorage was 16.7 inches. The months with the highest average rainfall were August and September, with August averaging 2.75 inches and September averaging 3.24 inches annually.
For snowfall, the average yearly snowfall between 2000 and 2022 was 76.4 inches. The highest snowfall occurred during the 2011–2012 season, with 134.5 inches, while the lowest snowfall was recorded in the 2015 season, with 25.1 inches.
Climate change
According to the ERA5 data from ECMWF, the average yearly temperature in Anchorage has risen from 0.8 °C in 1940 to 3.8 °C in 2022, an increase of 3 °C. In 2019, the mayor and city council of Anchorage created a climate action plan to address the expected effects of climate change on the city and its residents. The plan covers the entire Anchorage area, from Eklutna in the north to Portage in the south. A major goal of the plan is to cut greenhouse gas emissions by 80% by 2050 compared to 2008 levels. The first annual report about this plan was released in 2021. For short-term goals, the city also launched a plan called the "Municipality of Anchorage Climate Action Strategy."
Notable climate events
Because it is near active volcanoes, ash dangers happen sometimes, but not often. The most recent important event was an eruption of Mt. Spurr in August 1992. Mt. Spurr is 78 miles (126 kilometers) west of the city. The eruption caused about 3 millimeters (0.12 inches) of volcanic ash to fall on the city. Cleaning up the ash used a lot of water and created big problems for the Anchorage Water and Wastewater Utility.
On March 17, 2002, a storm brought 28.6 inches of snow, closing schools for two days. This storm set a new city record for the most snowfall in one day. It beat the previous record from March 16, 1955, which was 15.6 inches. The National Weather Service also recorded these snow measurements.