Climate averages 1991–2020

Anchorage weather
in September.

A cool, wet month: the 4th warmest and the wettest of the year.

Long-term climate patterns, not a forecast for a particular trip.

Average high 11.8°C Daytime mean, September

Average low 6.7°C Night-time mean, September

Rainfall 117 mm 15 days with ≥1 mm

Daylight 13 h Sunrise to sunset, per day

September is a cool month in Anchorage: daytime highs average 11.8°C and nights cool to about 6.7°C. By daytime temperature it is the 4th warmest of the 12 months.

Expect about 117 mm of rain on roughly 15 days, which makes September a wet month (the wettest month of the year). Daylight, from sunrise to sunset, lasts about 13 h 00 min on an average September day.

Among the 498 cities listed in the United States, Anchorage ranks 498th of 498 for the warmest September highs and joint 440th of 498 for the driest September (rainfall, lowest first). The mean September high of those 498 cities is 26.9°C; Anchorage is 15.1°C cooler than that mean.

From September to October, average highs fall by 7.4°C to 4.4°C, and monthly rainfall falls from 117 mm to 90 mm.

The annual picture

September in context

30-year average

Average highAverage low°C

Monthly precipitation

Average total · mm

Averages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated

Every month, side by side

Anchorage climate table

1991–2020

Monthly climate averages for Anchorage, 1991–2020
Month	Average highHigh / low	Average low	Precipitation mm/month	Wet days ≥1 mm/day	Daylight hours/dayDaylight h/day
January	-6.8°C-10.9°C	-10.9°C	50	10.4	6.56 h
February	-3.9°C-8.5°C	-8.5°C	50	9.7	8.99 h
March	-1.2°C-7.2°C	-7.2°C	38	8.5	11.712 h
April	4.7°C-1.8°C	-1.8°C	29	7.3	14.715 h
May	10.1°C2.9°C	2.9°C	30	7.1	17.417 h
June	15.4°C9.0°C	9.0°C	40	8.9	19.219 h
July	17.3°C11.9°C	11.9°C	73	12.5	18.418 h
August	16.3°C11.0°C	11.0°C	107	14.8	15.916 h
September, selected	11.8°C6.7°C	6.7°C	117	15.3	13.013 h
October	4.4°C-0.2°C	-0.2°C	90	13.2	10.110 h
November	-2.6°C-6.8°C	-6.8°C	66	11.7	7.47 h
December	-5.1°C-9.4°C	-9.4°C	73	12.9	5.66 h

Precipitation (rain or snow, as water) is the average of the 30 separate monthly totals. A wet day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.

Read the numbers correctly

Climate, not a promise.

These patterns help compare months. They cannot tell you the weather on a specific day of your trip.

Sources, method and limits

How these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Anchorage) is explained once on the Anchorage year overview and on the Sources, method and limits page.