This report describes the typical weather at the Alta Airport (Alta, Norway) weather station over the course of an average year. It is based on the historical records from 1985 to 2012. Earlier records are either unavailable or unreliable.
Alta has a humid subarctic continental climate with cool summers and no dry season. The area within 25 mi of this station is covered by tundra (57%), forests (23%), oceans and seas (12%), and grasslands (6%).
Over the course of a year, the temperature typically varies from 12°F to 63°F and is rarely below -4°F or above 74°F.
The warm season lasts from June 12 to September 4 with an average daily high temperature above 55°F. The hottest day of the year is July 23, with an average high of 63°F and low of 53°F.
The cold season lasts from November 15 to March 17 with an average daily high temperature below 31°F. The coldest day of the year is January 30, with an average low of 12°F and high of 23°F.
The length of the day varies significantly over the course of the year. The shortest day is December 21 with 0:00 hours of daylight; the longest day is June 20 with 24:00 hours of daylight.
Due to its extreme latitude, Alta experiences polar day (also known as the midnight Sun) during summer and polar night during winter. The precise start and end dates of polar day and night vary from year to year and depend on the precise location and elevation of the observer, and the local topography.
In summer, the Sun is continuously above the horizon for 69 days, from May 17 to July 25.
In winter, the Sun is continuously below the horizon for 52 days, from November 25 to January 16.
Daylight savings time (DST) is observed in this location during 2012, starting in the spring on March 25 and ending in the fall on October 28.
The median cloud cover ranges from 66% (partly cloudy) to 87% (mostly cloudy). The sky is cloudiest on September 6 and clearest on February 16. The clearer part of the year begins around November 14. The cloudier part of the year begins around April 17.
On February 16, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 44% of the time, and overcast or mostly cloudy 31% of the time.
On September 6, the cloudiest day of the year, the sky is overcast, mostly cloudy, or partly cloudy 71% of the time, and clear or mostly clear 11% of the time.
The probability that precipitation will be observed at this location varies throughout the year. Precipitation is most likely around February 1, occurring in 66% of days. Precipitation is least likely around August 12, occurring in 52% of days.
Over the entire year, the most common forms of precipitation are moderate snow, light snow, light rain, and moderate rain.
Moderate snow is the most severe precipitation observed during 28% of those days with precipitation. It is most likely around January 18, when it is observed during 34% of all days.
Light snow is the most severe precipitation observed during 26% of those days with precipitation. It is most likely around February 2, when it is observed during 29% of all days.
Light rain is the most severe precipitation observed during 24% of those days with precipitation. It is most likely around September 15, when it is observed during 29% of all days.
Moderate rain is the most severe precipitation observed during 17% of those days with precipitation. It is most likely around September 5, when it is observed during 21% of all days.
During the warm season, which lasts from June 12 to September 4, there is a 53% average chance that precipitation will be observed at some point during a given day. When precipitation does occur it is most often in the form of light rain (52% of days with precipitation have at worst light rain), moderate rain (37%), and drizzle (6%).
During the cold season, which lasts from November 15 to March 17, there is a 64% average chance that precipitation will be observed at some point during a given day. When precipitation does occur it is most often in the form of moderate snow (48% of days with precipitation have at worst moderate snow) and light snow (42%).
The likelihood of snow falling is highest around February 1, occurring in 63% of days. The season in which it is relatively likely for snow to fall spans from October 5 to May 15.
Either snow rarely accumulates at this location or snow depth measurements are unavailable or unreliable.
The relative humidity typically ranges from 51% (mildly humid) to 90% (very humid) over the course of the year, rarely dropping below 35% (comfortable) and reaching as high as 100% (very humid).
The air is driest around May 26, at which time the relative humidity drops below 58% (mildly humid) three days out of four; it is most humid around October 20, exceeding 86% (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 year, the dew point typically varies from 5°F (dry) to 52°F (very comfortable) and is rarely below -11°F (dry) or above 58°F (comfortable).
The time of the year between July 9 and August 12 is the most comfortable, with dew points that are neither too dry nor too muggy.
Over the course of the year typical wind speeds vary from 0 mph to 17 mph (calm to moderate breeze), rarely exceeding 28 mph (strong breeze).
The highest average wind speed of 9 mph (gentle breeze) occurs around January 23, at which time the average daily maximum wind speed is 17 mph (moderate breeze).
The lowest average wind speed of 7 mph (light breeze) occurs around September 13, at which time the average daily maximum wind speed is 13 mph (moderate breeze).