Historical Weather For 2012 in Stockholm, Sweden

Location

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%)

Calendar

Daylight saving time (DST) was observed at Stockholm during 2012. There were two time changes during 2012:

  • DST started on Sunday March 25, 2012 at 3:00 am, from CET (GMT+1) to CEST (GMT+2).
  • DST ended on Sunday October 28, 2012 at 2:00 am, from CEST (GMT+2) to CET (GMT+1).

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.

Temperature

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.

Temperature

The daily low (blue) and high (red) temperature during 2012 with the area between them shaded gray and superimposed over the corresponding averages (thick lines), and with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile). The bar at the top of the graph is red where both the daily high and low are above average, blue where they are both below average, and white otherwise.

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.

Hourly Temperature Bands

The full year of hourly temperature reports with the days of the year on the horizontal and the hours of the day on the vertical. The hourly temperature measurement is color coded into meaningful temperature bands: frigid is purple (below 15°F), freezing is blue (15°F to 32°F), cold is dark green (32°F to 50°F), cool is light green (50°F to 65°F), comfortable is yellow (65°F to 75°F), warm is light red (75°F to 85°F), hot is medium red (85°F to 100°F), sweltering is dark red (above 100°F), and missing data is pink.

Clouds

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.

Cloud Coverage

The fraction of time spent in each of the five sky cover categories over the course of 2012 on a daily basis. From top (most blue) to bottom (most gray), the categories are clear, mostly clear, partly cloudy, mostly cloudy, and overcast. Pink indicates missing data. Outside of the United States clear skies are often reported ambiguously, leading them to be lumped in with the missing data. The bar at the top of the graph is gray if the sky was cloudy or mostly cloudy for more than half the day, blue if it is clear or mostly clear for more than half the day, and blue-gray otherwise.

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.

Hourly Cloud Coverage

The full year of hourly cloud coverage reports with the days of the year on the horizontal and the hours of the day on the vertical. The sky cover is color coded: from most blue to most gray, the categories are clear, mostly clear, partly cloudy, mostly cloudy, and overcast. Pink indicates missing data. Outside of the United States clear skies are often reported ambiguously, leading them to be lumped in with the missing data.

Precipitation

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.

Present Weather Reports

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.

Precipitation Reports

The daily number of hourly observed precipitation reports during 2012, color coded according to precipitation type, and stacked in order of severity. From the bottom up, the categories are thunderstorms (orange); heavy, moderate, and light snow (dark to light blue); heavy, moderate, and light rain (dark to light green); and drizzle (lightest green). Not all categories are necessarily present in this particular graph. The faint shaded areas indicate climate normals. The bar at the top of the graph is green if any precipitation was observed that day and white otherwise.

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.

Hourly Weather Reports

The full year of hourly present weather reports with the days of the year on the horizontal and the hours of the day on the vertical. The color-coded categories are thunderstorms (orange); heavy, moderate, and light snow (dark to light blue); heavy, moderate, and light rain (dark to light green); drizzle (lightest green); freezing rain and sleet (light and dark cyan); snow grains (lightest blue); hail (red); fog (gray); and haze (brownish gray).

Liquid Precipitation Reports

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.

Liquid Precipitation Reports

The daily number of hourly observed liquid precipitation reports (including thunderstorms) during 2012, with climate normals (faint shaded areas). The bar at the top of the graph is green if any liquid precipitation was observed that day and white otherwise.

Snow

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.

Reports

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.

Snow Reports

The daily number of hourly observed snow reports during 2012, with climate normals (faint shaded areas). The bar at the top of the graph is blue if there was snow fall observed that day and white otherwise.

Humidity

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.

Humidity

The daily low (brown) and high (blue) relative humidity during 2012 with the area between them shaded gray and superimposed over the corresponding averages (thick lines), and with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).

Dew 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.

Dew Point

The daily low (blue) and high (red) dew point during 2012 with the area between them shaded gray and superimposed over the corresponding averages (thick lines), and with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).

Wind

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.

Wind Speed

The daily low and high wind speed (light gray area) and the maximum daily wind gust speed (tiny blue dashes).

Visibility

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.

Visibility

The daily average visibility, depicted as gray bars encroaching down from the top of the graph.

Cloud Ceiling

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'.

Cloud Ceiling

The daily average cloud ceiling, depicted as gray bars encroaching down from the top of the graph. Missing data or days with insufficient clouds to define a cloud ceiling are shown as white columns.