This autumn — the months stretching from September to November — was either unusually or exceptionally warm across most of the country, according to the FMI.
Kotka's Rankki observation station, for example, recorded the warmest autumn in its more than 90-year history.
FMI meteorologist Pauli Jokinen said the national average temperature this autumn was the fourth mildest in Finland's measurement history.
"Autumn 2020 was the warmest on record, only about 0.17 degrees warmer than this autumn," he explained.
Meteorologists use the term "exceptional" when a weather phenomenon has a statistical likelihood of occurring on average three times every hundred years or less.
A "rare" phenomenon occurs less frequently than once every ten years on average.
The weather in Finland this autumn has been remarkable in many ways. Northern Lapland saw record-high seasonal temperatures in November, while storms with near-hurricane winds swept through half of the country at the end of last month.