When to Change Tires: Dates by Law and by Weather
A tool for deciding when to change tires where you live: it shows which tires the law of your country allows today, and from the forecast and the last ten seasons it works out when the daily mean temperature will steadily cross +7 °C (45 °F). Winter and summer tire dates, studded tire windows and fines come with links to the legal texts.
How to use
Search for it or press "My location".
At the top — what is allowed today; below — when the forecast turns cold.
Download the .ics file and your calendar will remind you on the day.
Find out if it is time to switch to winter or summer tires
When to change tires
In the U.S. there is no federal winter tire law: studded tire dates and traction rules are set by each state — Washington, Oregon, New York, Pennsylvania, Minnesota, Colorado and Alaska are covered here.
Pick a city — the tool will tell you if the weather says it is time to change tires and show the rules for that place.
What is allowed today
Weather
Temperature: three weeks and the forecast
Rules by month
Law
How "time to change" is worked out
Threshold. Michelin writes that for a tire winter starts at 7 °C (45 °F): below it summer rubber hardens and grips worse; Russia's Ministry of Transport advises a daily mean of +5 to +7 °C. The tool uses +7 °C by default; the switch sets +5 °C.
"Steady" means five days in a row on the other side of the threshold. Five days is the usual climatologists' rule for the start of a season: one cold day in September is not fall yet. A short warm spell after that does not cancel the date — only one that lasts five days or more and brings more warmth than the cold built up since the cooling began.
Weather. Past days come from NASA POWER and the nearest airport, the next 9–10 days from two forecast models, MET Norway and Germany's DWD; when they disagree, the date is a range. Nobody honestly knows the weather beyond the forecast, so the usual date is shown next to it — the median of the last ten seasons at this place, with the earliest and latest.
Checked. In October and April the NASA grid (about 50 km) is usually 0.5–3 °C colder than a city weather station. We compared crossing dates from the grid and from 14 stations in Russia, Ukraine, Belarus, Kazakhstan and Germany for 2015–2025: the median difference is 1 day in fall and 2 days in spring; in 8 cases of 10 it is no more than 12 and 17 days.
Markings, tread, tire age
- M+S (M&S, M S) means "mud and snow": the maker marks a tread pattern designed for mud and snow, and the marking needs no snow test. That is why Germany has accepted only snowflake tires as winter tires since October 2024.
- The snowflake on a three-peak mountain (3PMSF, the Alpine symbol) goes on tires that passed a snow test against a reference tire under UN Regulation No. 117; in Canada the snow traction index must be at least 110.
- Under the EAEU rule a tire with the mountain snowflake or M+S counts as a winter tire, so marked all-season tires meet the December–February rule there.
- The minimum tread for cars is 1.6 mm in the EAEU, Germany, Spain, the UK, Ukraine and Brazil. Winter tires on snow and ice need more than 4 mm in the EAEU, at least 4 mm in Austria and at least 3.5 mm on British Columbia's routes.
- The date of manufacture is the last four digits of the DOT code on the sidewall: two for the week and two for the year (3421 is week 34 of 2021). Three-digit codes were used before 2000.
The tool is a guide, not legal advice. Rules were checked against the legal texts on October 23, 2026 and may change; a forecast more than a few days out is uncertain. The decision is the driver's: on ice and snow summer tires are dangerous whatever the calendar says.
Forecast — MET Norway (CC BY 4.0) and DWD; past days and the last ten seasons — NASA POWER; airport observations — aviationweather.gov.