This report describes the typical weather at the Juneau International Airport (Juneau, Alaska, United States) weather station over the course of an average August. It is based on the historical records from 1974 to 2012. Earlier records are either unavailable or unreliable.
Juneau, Alaska has a mild humid temperate climate with warm summers and no dry season. The area within 25 mi of this station is covered by tundra (37%), oceans and seas (34%), and forests (28%).
The month of August is characterized by falling daily high temperatures, with daily highs ranging from 64°F to 59°F over the course of the month, exceeding 74°F or dropping below 53°F only one day in ten.
Over the course of August, the length of the day is very rapidly decreasing. From the start to the end of the month, the length of the day decreases by 2:24 hours, implying an average day-over-day decrease of 4.6 minutes.
The shortest day of the month is August 31 with 14:02 hours of daylight; the longest day is August 1 with 16:26 hours of daylight.
The earliest sunrise is at 4:51am on August 1; the latest sunset is at 9:17pm on August 1; the latest sunrise is at 5:57am on August 31; the earliest sunset is at 7:59pm on August 31.
Daylight saving time is observed in 2012 but it neither starts nor ends in August, so the entire month is in daylight time.
The median cloud cover is 100% (overcast) and does not vary substantially over the course of the month.
On August 16, a representative day, the sky is clear or mostly clear 15% of the time, partly cloudy 8% of the time, and mostly cloudy or overcast 76% of the time.
The probability that precipitation will be observed at this location varies throughout the month. Precipitation is most likely around August 31, occurring in 73% of days. Precipitation is least likely around August 1, occurring in 68% of days.
Throughout August, the most common forms of precipitation are light rain and moderate rain.
Light rain is the most severe precipitation observed during 61% of those days with precipitation. It is most likely around August 10, when it is observed during 44% of all days.
Moderate rain is the most severe precipitation observed during 32% of those days with precipitation. It is most likely around August 30, when it is observed during 25% of all days.
Either snow is exceptionally unlikely to fall at this location in August or this station does not reliably report precipitation types.
The relative humidity typically ranges from 66% (mildly humid) to 97% (very humid) over the course of a typical August, rarely dropping below 45% (comfortable) and reaching as high as 100% (very humid).
The air is driest around August 7, at which time the relative humidity drops below 79% (humid) three days out of four; it is most humid around August 30, rising above 96% (very humid) three days out of four.
Dew point is often a better measure of how comfortable a person will find the weather than relative humidity because it more directly relates to whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid.
Over the course of a typical August, the dew point typically varies from 45°F (dry) to 55°F (very comfortable) and is rarely below 39°F (dry) or above 58°F (comfortable).
The time of the month between August 1 and August 31 is the most comfortable, with dew points that are neither too dry nor too muggy.
Over the course of August typical wind speeds vary from 0 mph to 13 mph (calm to moderate breeze), rarely exceeding 21 mph (fresh breeze).
The highest average wind speed of 7 mph (light breeze) occurs around August 31, at which time the average daily maximum wind speed is 13 mph (moderate breeze).
The lowest average wind speed of 7 mph (light breeze) occurs around August 4, at which time the average daily maximum wind speed is 12 mph (gentle breeze).