Winter tyre rules in Finland

They are, but the condition has two parts: the month and the road conditions. Section 105 of the Road Traffic Act (tieliikennelaki) reads: "Jos sää tai keli sitä edellyttää, marras-, joulu-, tammi-, helmi- ja maaliskuun aikana on käytettävä talvirenkaita, joiden kulutuspinnan pääurien syvyys on vähintään 3,0 millimetriä". In English: if the weather or road conditions require it, during November, December, January, February and March tyres must be used whose main tread grooves are at least 3.0 millimetres deep. Winter tyres are therefore mandatory only during those five months, and even then only when conditions require it.

Before June 2020 the rule was a pure calendar rule: winter tyres had to be used throughout December, January and February regardless of conditions (Decree on the use of vehicles on the road, 1257/1992, repealed on 1 June 2020). The current Road Traffic Act (729/2018, in force from 1 June 2020) widened the season from November to March and handed the decision to the conditions and the driver.

From April to October the law does not require winter tyres at all. What remains are the general requirements for a tyre (main grooves at least 1.6 mm, section 104) and the road user's duty to observe "the care and caution required by the circumstances" (section 3). A freezing October night therefore falls outside section 105, even though an icy road is equally slippery on either side of that line.

The law names neither a date nor a place; it leaves the judgement to the driver. That is what this service answers: the map shows, municipality by municipality, where in Finland the road surface is heading below freezing in the coming days.

From November to March you may move to summer tyres once conditions no longer require winter tyres: the law names no date that opens the change mid-season. From 1 April the winter tyre requirement ends entirely, because section 105 no longer covers April. The same day also closes the studded tyre season, though studs keep a weather-based exception.

A date still tells you nothing about the conditions. Traficom, the Finnish Transport and Communications Agency, advises changing tyres according to the weather and road conditions and recommends replacing a winter tyre at around 5 mm of tread, even though the law allows down to 3.0 mm.

A return of winter is ordinary in Finland, and one warm week does not yet mean spring. That is why the map does not turn green on the strength of a single mild day: it waits until no freezing night is left anywhere in the forecast period.

The studded tyre window is the part of the winter tyre rules that is based on the calendar. Under section 106 of the Road Traffic Act, studded tyres may be used

• from 1 November to 31 March, in the words of the law "marraskuun alusta maaliskuun loppuun";
• outside that window too, "jos sää tai keli sitä edellyttää" (if the weather or road conditions require it). October snowfall or a return of winter in April does not make studs illegal.

An end date tied to Easter is still widely believed in, and it was once true: under the repealed Decree 1257/1992 the season ran to the Monday following Easter Monday if that fell after 31 March. In the law now in force the date is 31 March, and Easter is not mentioned at all (why it was removed).

The map shows the season for every municipality and states whether a weather-based exception is in force right now where you are driving.

The law does not rank studded tyres above friction tyres or the reverse: both satisfy the winter tyre requirement. The choice depends on the conditions you drive in, although a friction tyre now has to carry a snow grip marking. For studs, section 106 additionally requires that they be fitted to all wheels of a passenger car, van or special vehicle and of a trailer up to 3.5 tonnes, so studding only some wheels is not an option.

Because the months and the conditions exception settle different questions. Inside the window studded tyres are allowed unconditionally, and no reason has to be given to anyone. Outside the window their use is conditional: it is one of the five exceptions in the second subsection of section 106, and the condition has to be met where and when you are driving.

Nor is the restriction aimed at road safety but at the road surface: the section permits studs and other anti-skid devices "that do not substantially damage the road surface". During the law's preparation the Ministry of the Environment warned that extending the winter tyre season would increase the distance driven on studded tyres and lead to "greater formation of street dust and wear of road surfaces" (Government proposal HE 180/2017 vp). Wear and dust are national totals that an individual driver's judgement about conditions cannot limit; the season does that. The exception, in turn, makes sure the season does not force anyone onto the wrong tyres on a single icy day.

The Easter rule was removed on exactly this logic. According to the government proposal it would be "poistettaisiin monimutkaisena" (removed as complicated). A moving date had been needed because at Easter people travel from the south to the north, where winter may still be under way. That situation is now handled by the conditions exception, which reaches the same outcome under a simpler rule.

When winter tyres must be used, the depth of their main grooves has to be at least 3.0 millimetres (section 105). The general year-round minimum for tyres is 1.6 mm, and 1.0 mm for a motorcycle (section 104). A winter tyre is therefore held to nearly twice the groove depth.

There is a practical reason for the difference: a winter tyre's grooves are the space slush and water escape into from under the tyre. A worn winter tyre can meet the general 1.6 mm requirement and still fall below the limit required of a winter tyre. Traficom recommends changing at around 5 mm of tread, well before the legal limit.

A winter tyre must also carry a marking. Under Traficom's regulation Ajoneuvojen käyttö tiellä (Use of vehicles on the road, point 2.1), a tyre counts as a winter tyre for a passenger car, van or special vehicle if it carries the three-peak mountain snowflake marking 3PMSF, the POR marking approved for off-road use, or if it is a studded tyre. The M+S marking alone is no longer enough: it was accepted during a transition period until 30 November 2024 (until 30 November 2029 for a tyre on an O2-class trailer). On an older friction tyre it is worth checking the sidewall marking as well as the tread.

The winter tyre requirement does not apply to the towing vehicle alone. From November to March, when conditions require it, winter tyres must also be used on a trailer whose classification or coupling mass is over 0.75 tonnes and at most 3.5 tonnes (section 105, subsection 1, point 5). A light trailer under 750 kg falls outside the requirement; heavier combinations come under the second subsection of the same section, which requires 5.0 mm of tread on the driving axles of a lorry or bus and 3.0 mm on the others and on the trailer.

For studs the rule runs differently from what is often assumed: "Jos vetoautossa on nastarenkaat, luokittelumassaltaan yli 0,75 tonnin ja enintään 3,5 tonnin painoisessa auton perävaunussa on käytettävä talvirenkaita" (section 106): if the towing vehicle has studded tyres, a trailer of over 0.75 and at most 3.5 tonnes must use winter tyres. Studs on the towing vehicle therefore oblige the trailer to have winter tyres, not studs.

The law states the rule. When that rule bites where you are driving depends on the conditions, and conditions vary by hundreds of kilometres on the same day.

• The map of the whole country, 309 municipalities
• Winter tyres in Helsinki
• Winter tyres in Tampere
• Winter tyres in Turku
• Winter tyres in Oulu
• Winter tyres in Rovaniemi