Average Weather in Norrtälje Sweden

In Norrtälje, the summers are short, comfortable, and partly cloudy and the winters are long, freezing, dry, windy, and mostly cloudy. Over the course of the year, the temperature typically varies from 23°F to 70°F and is rarely below 7°F or above 78°F.

The warm season lasts for 2.9 months, from June 9 to September 5, with an average daily high temperature above 62°F. The hottest day of the year is July 22, with an average high of 70°F and low of 55°F.

The cold season lasts for 4.1 months, from November 21 to March 23, with an average daily high temperature below 40°F. The coldest day of the year is February 11, with an average low of 23°F and high of 32°F.

The figure below shows you a compact characterization of the entire year of hourly average temperatures. The horizontal axis is the day of the year, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

Average Hourly Temperature

The average hourly temperature, color coded into bands: frigid < 15°F < freezing < 32°F < chilly < 45°F < cold < 55°F < cool < 65°F < comfortable < 75°F < warm < 85°F < hot < 95°F < sweltering. The shaded overlays indicate night and civil twilight.

Clouds

In Norrtälje, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.

The clearer part of the year in Norrtälje begins around April 22 and lasts for 5.6 months, ending around October 9. On July 7, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 58% of the time, and overcast or mostly cloudy 42% of the time.

The cloudier part of the year begins around October 9 and lasts for 6.4 months, ending around April 22. On November 27, the cloudiest day of the year, the sky is overcast or mostly cloudy 73% of the time, and clear, mostly clear, or partly cloudy 27% of the time.

Cloud Cover

The percentage of time spent in each cloud cover band, categorized by the percentage of the sky covered by clouds: clear < 20% < mostly clear < 40% < partly cloudy < 60% < mostly cloudy < 80% < overcast.

Precipitation

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Norrtälje varies throughout the year.

The wetter season lasts 6.8 months, from June 9 to January 4, with a greater than 23% chance of a given day being a wet day. The chance of a wet day peaks at 29% on November 13.

The drier season lasts 5.2 months, from January 4 to June 9. The smallest chance of a wet day is 16% on March 14.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 27% on August 20.

Daily Chance of Precipitation

The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).

Rainfall

To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. Norrtälje experiences some seasonal variation in monthly rainfall.

Rain falls throughout the year in Norrtälje. The most rain falls during the 31 days centered around August 6, with an average total accumulation of 2.0 inches.

The least rain falls around February 20, with an average total accumulation of 0.5 inches.

Average Monthly Rainfall

The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average liquid-equivalent snowfall.

Snowfall

We report snowfall in liquid-equivalent terms. The actual depth of new snowfall is typically between 5 and 10 times the liquid-equivalent amount, assuming the ground is frozen. Colder, drier snow tends to be on the higher end of that range and warmer, wetter snow on the lower end.

As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day of the year. Norrtälje experiences some seasonal variation in monthly liquid-equivalent snowfall.

The snowy period of the year lasts for 4.8 months, from November 12 to April 7, with a sliding 31-day liquid-equivalent snowfall of at least 0.1 inches. The most snow falls during the 31 days centered around January 23, with an average total liquid-equivalent accumulation of 0.3 inches.

The snowless period of the year lasts for 7.2 months, from April 7 to November 12. The least snow falls around July 25, with an average total liquid-equivalent accumulation of 0.0 inches.

Average Liquid-Equivalent Monthly Snowfall

The average liquid-equivalent snowfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average rainfall.

Sun

The length of the day in Norrtälje varies extremely over the course of the year. In 2017, the shortest day is December 21, with 5 hours, 57 minutes of daylight; the longest day is June 21, with 18 hours, 47 minutes of daylight.

Hours of Daylight and Twilight

The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

The earliest sunrise is at 3:23 AM on June 19, and the latest sunrise is 5 hours, 23 minutes later at 8:46 AM on December 27. The earliest sunset is at 2:40 PM on December 16, and the latest sunset is 7 hours, 30 minutes later at 10:10 PM on June 23.

Daylight saving time (DST) is observed in Norrtälje during 2017, starting in the spring on March 26, lasting 7.1 months, and ending in the fall on October 29.

Sunrise & Sunset with Twilight and Daylight Saving Time

The solar day over the course of the year 2017. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray. The transitions to and from daylight saving time are indicated by the 'DST' labels.

Humidity

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

The perceived humidity level in Norrtälje, as measured by the percentage of time in which the humidity comfort level is muggy, oppressive, or miserable, does not vary significantly over the course of the year, staying within 1% of 1% throughout.

Humidity Comfort Levels

The percentage of time spent at various humidity comfort levels, categorized by dew point: dry < 55°F < comfortable < 60°F < humid < 65°F < muggy < 70°F < oppressive < 75°F < miserable.

Wind

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed in Norrtälje experiences mild seasonal variation over the course of the year.

The windier part of the year lasts for 6.4 months, from September 8 to March 21, with average wind speeds of more than 4.6 miles per hour. The windiest day of the year is December 31, with an average hourly wind speed of 5.5 miles per hour.

The calmer time of year lasts for 5.6 months, from March 21 to September 8. The calmest day of the year is June 25, with an average hourly wind speed of 3.7 miles per hour.

Average Wind Speed

The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.

The predominant average hourly wind direction in Norrtälje varies throughout the year.

The wind is most often from the south for 6.7 months, from March 9 to September 29, with a peak percentage of 37% on July 24. The wind is most often from the west for 5.4 months, from September 29 to March 9, with a peak percentage of 43% on January 1.

Wind Direction

The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions (north, east, south, and west), excluding hours in which the mean wind speed is less than 1 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Water Temperature

Norrtälje is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.

The average water temperature experiences significant seasonal variation over the course of the year.

The time of year with warmer water lasts for 2.5 months, from July 2 to September 16, with an average temperature above 56°F. The day of the year with the warmest water is August 7, with an average temperature of 62°F.

The time of year with cooler water lasts for 4.6 months, from December 14 to May 3, with an average temperature below 39°F. The day of the year with the coolest water is March 1, with an average temperature of 33°F.

Average Water Temperature

The daily average water temperature (purple line), with 25th to 75th and 10th to 90th percentile bands.

Solar Energy

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy experiences extreme seasonal variation over the course of the year.

The brighter period of the year lasts for 3.2 months, from May 4 to August 10, with an average daily incident shortwave energy per square meter above 5.0 kWh. The brightest day of the year is June 28, with an average of 6.3 kWh.

The darker period of the year lasts for 4.4 months, from October 15 to February 27, with an average daily incident shortwave energy per square meter below 1.4 kWh. The darkest day of the year is December 20, with an average of 0.2 kWh.

Average Daily Incident Shortwave Solar Energy

The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

Topography

For the purposes of this report, the geographical coordinates of Norrtälje are 59.758 deg latitude, 18.705 deg longitude, and 66 ft elevation.

The topography within 2 miles of Norrtälje contains only modest variations in elevation, with a maximum elevation change of 174 feet and an average elevation above sea level of 70 feet. Within 10 miles also contains only modest variations in elevation (233 feet). Within 50 miles also contains only modest variations in elevation (413 feet).

The area within 2 miles of Norrtälje is covered by trees (30%), artificial surfaces (29%), cropland (24%), and water (15%), within 10 miles by trees (56%) and cropland (23%), and within 50 miles by water (53%) and trees (30%).

Data Sources

This report illustrates the typical weather in Norrtälje, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.

Temperature and Dew Point

There are 2 weather stations near enough to contribute to our estimation of the temperature and dew point in Norrtälje.

For each station, the records are corrected for the elevation difference between that station and Norrtälje according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.

The estimated value at Norrtälje is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Norrtälje and a given station.

The stations contributing to this reconstruction are: Stockholm Arlanda Airport (69%, 46 kilometers, west) and Mariehamn Airport (31%, 78 kilometers, northeast).

Other Data

All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Tables of the Sun, Moon and Planets , by Jean Meeus.

All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.

Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.

Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.

Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .

Time zones for aiports and weather stations are provided by AskGeo.com .

Maps are © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.