So when is it actually spring in Sweden? For many people, spring begins when the snow disappears, the sun warms your cheeks, and the winter jacket suddenly feels unnecessary. In Sweden, people often take the chance to shed some layers as soon as it gets a little warmer, which is understandable since we’re not exactly spoiled with sunshine and warmth. But meteorologically, the definition is much stricter than that. The Swedish Meteorological and Hydrological Institute (SMHI) bases it on the daily mean temperature, not on how it feels outside.
According to SMHI, spring arrives when the daily mean temperature stays above 0.0°C for seven days in a row. The official arrival date of spring is counted as the first of those seven days. This means that spring is always determined afterwards, once a full week of spring-like temperatures has passed.
SMHI has also set clear limits for when spring can officially begin. February 15 is the earliest possible date for spring to arrive, and July 31 is the latest. This means that an unusually mild week in January can’t officially bring spring to Sweden, no matter how eager people might be to put their winter hats away.
Spring Can’t Go Back
There’s also one detail that surprises many people: once spring has officially arrived according to SMHI, it can’t “go back.” Even if the cold returns later, it’s still considered spring from a meteorological standpoint. This highlights one of the differences between how we experience the weather in everyday life and how seasons are defined in meteorology.
SMHI also explains that this method is used to determine the arrival of spring during a specific year. For climatological averages, a different definition is used. In that case, spring is linked to a rising daily mean temperature that stays between 0.0°C and 10.0°C.
In Sweden, spring requires patience: seven days in a row and a stamp of approval from SMHI. A bit bureaucratic, perhaps, but also very Swedish!
Source: SMHI
