This report describes the historical weather record at the Stockholm-Arlanda Airport (Stockholm, Sweden) during 2012. This station has records back to March 2006.
Stockholm has a humid continental climate with warm summers and no dry season. The area within 25 mi of this station is covered by forests (75%), lakes and rivers (11%), built-up areas (7%), oceans and seas (4%), and croplands (3%)
Daylight saving time (DST) was observed at Stockholm during 2012. There were two time changes during 2012:
2012 was a leap year and thus has 366 days rather than the normal 365. Leap years occur every fourth year and the extra day is always February 29th. In 2012 February 29th falls on a Wednesday.
The summer and winter solstices and the spring and fall equinoxes mark the passing of the seasons. They fall on nearly the same day each year, with differences of a day or two depending on the year. In 2012 they occurred on:
|Spring Equinox||Tuesday, 20 March 2012.|
|Summer Solstice||Wednesday, 20 June 2012.|
|Fall Equinox||Saturday, 22 September 2012.|
|Winter Solstice||Friday, 21 December 2012.|
The hottest day of 2012 was July 25, with a high temperature of 81°F. For reference, on that day the average high temperature is 73°F and the high temperature exceeds 79°F only one day in ten. The hottest month of 2012 was July with an average daily high temperature of 71°F.
Relative to the average, the hottest day was March 22. The high temperature that day was 61°F, compared to the average of 42°F, a difference of 19°F. In relative terms the warmest month was March, with an average high temperature of 46°F, compared to an typical value of 40°F.
The longest warm spell was from February 17 to March 4, constituting 17 consecutive days with warmer than average high temperatures. The month of March had the largest fraction of warmer than average days with 71% days with higher than average high temperatures.
The coldest day of 2012 was February 4, with a low temperature of -2°F. For reference, on that day the average low temperature is 20°F and the low temperature drops below 9°F only one day in ten. The coldest month of 2012 was February with an average daily low temperature of 17°F.
Relative to the average, the coldest day was December 3. The low temperature that day was -0°F, compared to the average of 29°F, a difference of 30°F. In relative terms the coldest month was December, with an average low temperature of 20°F, compared to an typical value of 26°F.
The longest cold spell was from November 29 to December 15, constituting 17 consecutive days with cooler than average low temperatures. The month of December had the largest fraction of cooler than average days with 68% days with lower than average low temperatures.
The longest freezing spell was from January 30 to February 12, constituting 14 consecutive days with temperatures strictly below freezing.
This station did not reliably report the cloud coverage during 2012 but there is enough reported data to warrant the inclusion of the following graphs.
The cloudiest month of 2012 was December, with 84% of days being more cloudy than clear. The longest spell of cloudy weather was from December 10 to December 28, constituting 19 consecutive days that were cloudier than they were clear.
This station provides hourly reports of significant weather events at and around the station, but does not report the quantity of precipitation at the station itself. This is common for weather stations located outside of the United States, and for a small subset of stations in the United States that are located at lesser used and smaller airports.
This station reports when significant weather events (including precipitation) are visually observed at or near the station. Such events do not always correspond to measured quantities of liquid equivalent precipitation, such as when the event is near by not at the station, or in the case of solid precipitation that does not melt in the collection basin.
The day in 2012 with the most precipitation observations was September 22. There were 24 hourly weather reports that day (out of a maximum of 24) in which some form of precipitation was observated at or near the station. The month with the most precipitation observations was December, with 357 hourly present weather reports involving some form of precipitation.
As determined by the present weather reports, the longest dry spell was from February 29 to March 8, constituting 9 consecutive days with no observed precipitation. The month with the largest fraction of days without observed precipitation was March, with 61% of days reporting no observed precipitation at all.
The month with the largest fraction of days with at least some observed precipitation was December, with 97% of days reporting some observed precipitation.
In this section we consider only those weather reports that indicate liquid precipitation. For the purposes of this analysis, we include thunderstorms even though some thunderstorms are not accompanied by liquid precipitation.
The month of 2012 with the largest number of those reports was October, with a total of 138 reports. The day with the largest number of those reports was September 22, with a total of 24 reports.
This station reports when snow is observed falling but does not report the quantity of snow that has fallen or the depth of snow on the ground.
In this section we consider hourly weather reports that contain an observation of falling snow. These reports do not necessarily correspond to accumulation.
The first reported snow fall in 2012 was on October 25; the last was on April 20. The month of 2012 with the largest number of those reports was December, with a total of 298 reports. The day with the largest number of those reports was November 29, with a total of 24 reports.
Humidity is an important factor in determining how weather conditions feel to a person experiencing them. Hot and humid days feel even hotter than hot and dry days because the high level of water content in humid air discourages the evaporation of sweat from a person's skin.
When reading the graph below, keep in mind that the hottest part of the day tends to be the least humid, so the daily low (brown) traces are more relevant for understanding daytime comfort than the daily high (blue) traces, which typically occur during the night. Applying that observation, the least humid month of 2012 was May with an average daily low humidity of 39%, and the most humid month was December with an average daily low humidity of 88%.
But it is important to keep in mind that humidity does not tell the whole picture and the dew point is often a better measure of how comfortable a person will find a given set of weather conditions. Please see the next section for continued discussion of this point.
Dew point is the temperature below which water vapor will condense into liquid water. It is therefore also related to the rate of evaporation of liquid water. Since the evaporation of sweat is an important cooling mechanism for the human body, the dew point is an important measurement for understanding how dry, comfortable, or humid a given set of weather conditions will feel.
Generally speaking, dew points below 50°F will feel a bit dry to some people, but comfortable to people accustomed to dry conditions; dew points from 50°F to 68°F are fairly comfortable to most people, and dew points above 68°F are increasingly uncomfortable, becoming oppressive around 77°F.
To take some examples, and basing our categorization on the daily high dew point in 2012, January had 31 dry days, no comfortable days, and no humid days; April had 30 dry days, no comfortable days, and no humid days; July had no dry days, 31 comfortable days, and no humid days; and October had 22 dry days, 9 comfortable days, and no humid days.
The highest sustained wind speed was 31 mph, occurring on March 10; the highest daily mean wind speed was 23 mph (December 5); and the highest wind gust speed was 48 mph (March 25).
The windiest month was November, with an average wind speed of 11 mph. The least windy month was August, with an average wind speed of 8 mph.
Visibility is the maximum distance at which a given reference object or light can be clearly discerned. In the United States, visibilities that are greater than or equal to 10 miles are typically reported as 10 miles.
The day of 2012 with the lowest average visibility was November 4, with an average visibility of 0.7 mi. The month with the lowest average visibility was December, with an average visibility of 5.0 mi. With an average visibility of 6.0 mi, the month of May had the highest average visibility.
The cloud ceiling is the altitude of the lowest layer of clouds that are at categorized as broken (mostly cloudy) or overcast (cloudy). If no such cloud layer exists then the ceiling is unlimited and no value is reported.
The day of 2012 with the lowest average cloud ceiling was April 16, with an average cloud ceiling of 200'. The month with the lowest average cloud ceiling was November, with an average cloud ceiling of 2310'. The month of May has the highest average cloud ceiling, with an average cloud ceiling of 6320'.