About the data

Sources

All measurements come from SMHI's open meteorological observations. Temperaturkollen processes the data and is not an official SMHI service. For each station we use four parameters:

• Parameter 1: air temperature, momentary value once an hour. Used for "right now".
• Parameter 2: daily mean temperature for the calendar day 00–24 UTC.
• Parameter 19 and 20: the day's lowest and highest temperature, measured over 18–18 UTC and filed under the day on which that window ends.

Official monthly and annual normals for 1991–2020 come from SMHI's normal values file. For stations with shorter series SMHI estimates part of the normal; it still counts as SMHI's official normal.

Licence: SMHI Open Data is published under Creative Commons Attribution 4.0 (CC BY 4.0). Source: SMHI. Temperaturkollen has processed the data as described on this page.

Quality and plausibility

Both quality codes in the daily series count: G (checked and approved values) and Y (suspect or aggregated values, roughly checked archive data and unchecked real-time data), as SMHI defines them in its data files. Values marked Y are not singled out on the site. Values with an unknown code, empty values and values outside −55 °C to +40 °C are not used, and the number rejected per station and parameter is logged at import. If a day's minimum is higher than its maximum both are discarded. The mean is not checked against the minimum and maximum, because they cover different windows.

SMHI's reviewed archive ends about three months back. Newer days come from SMHI's latest months, which are not yet fully reviewed. When the archive covers a day, its value replaces the earlier one.

Days

"Today" is decided in Swedish time (Europe/Stockholm). Today's daily mean does not exist until tomorrow, so daily series never include days after yesterday. Because the mean covers 00–24 UTC and the minimum and maximum 18–18 UTC, a daily mean outside that day's minimum and maximum is legitimate. The three series are never mixed.

Coverage

With at least 90% of the days measured, a value is complete. Between 50% and 90% it is shown as partial, with "X of Y days". Below 50% no value is shown.

Means

• Temperatures are always averaged as arithmetic means, never added up.
• 7-day mean: the day and the 6 calendar days before it, with at least 5 valid days.
• Monthly mean: by coverage. For the current month only days up to the latest observation count, marked "so far".
• Annual mean: only when all 12 months are complete.

Daily reference 1991–2020

For each calendar day we take the mean of all valid daily means from 1991–2020 that fall within 7 calendar days either side of it. The value is used only if it rests on at least 300 daily values from at least 24 different years. If fewer than 360 of the 366 calendar days meet that requirement, the station gets no normal curve at all.

The daily reference is always labelled "calculated reference 1991–2020 (SMHI data)". Official monthly normals are never stretched into daily values. For whole months we compare with the official monthly normal; without one, the monthly mean of the daily reference is used and labelled "calculated".

Comparisons

Days are compared by calendar date on 366 places including 29 February. Between two years, 29 February counts only when both years have it; against the normal it counts when the main year has it. The comparison year gets the same calendar window as the main year, and when the current year is involved the window is cut at the last observed day for both years. The difference against the comparison year is averaged over days where both have a value.

Stations

One series is one station; stations are never spliced. Only stations that publish a daily mean are candidates. A place gets the station with the shortest distance plus a penalty in kilometres for a short series or a missing official normal, within 80 km, among active stations that have reported within 21 days. If another station within 30 km covers earlier years, a link to it is shown.

"Right now" is the latest hourly value from the history station if it is at most 180 minutes old; otherwise from the nearest station within 50 km with such a fresh value, named with its distance; otherwise the last known value, marked as out of date.

Updates

• Hourly values: every hour.
• Daily values from the latest months: at 07 and 13 Swedish time.
• Reviewed archive: checked once a day and fetched again for stations that SMHI has marked as updated.
• Station list: once a day. Normals: once a week.

Limitations

• Most places have no station of their own. The values come from the station named on each page.
• A station that has moved can show level shifts; stations that have moved 2 times or more carry a warning.
• Stations with short series may lack a daily reference curve.
• Means, deviations and rankings are calculated by Temperaturkollen and are not official SMHI statistics.
• We make no trend claims from our own station data and show no forecasts.