The Soviets didn't like Fagerholm's cabinet, because it included Väinö Leskinen and Olavi Lindblom (Social Democrats). Especially because they were chosen as the contribution of Väinö Tanner (Social Democratic Party chairman, guilty of war according to the Soviets).

And then the Soviets were also hurt because Finland didn't grant a Visa to Otto Ville Kuusinen (Finnish, later Soviet politician, literary historian, and poet. Also the Prime Mister and Minister of Foreign Affairs of the puppet goverment of Finland in 1939). The Communist Party of Finland had the 40th anniversary celebration and he couldn't participate. That wasn't the most important reason, but showed that Finland hadn't forget the Winter War.

At first pressure against Finland was economical, then the Soviet Ambassador to Helsinki (Viktor Lebedev) left suddenly to a vacation. He didn't even visit foreign minister of Finland, which was against the protocol. Then the Soviets informed that Lebedev isn't coming back, and they aren't goint to appoint a successor. Diplomatic relations were cut.

Later Hubert Humphrey offered economical help from the United States to Finland, but Finland needed to decline because it would have caused more harm than good. Humphrey also discussed with Khrushchev about this economical pressure, but Khrushchev just pretended he doesn't understand what he means.

The crisis was solved when Urho Kekkonen (Finnish president) "randomly" met Nikita Khrushchev and Andrei Gromyko in Leningrad. According to Khrushchev, the whole crisis was because behind Fagerholm's broad back they saw hostile characters of Tanner, Leskinen, Lindblom and Pitsing. He also said, that Finland has the right to choose their goverment, but the Soviet Union also has the right to show what it thinks about it.

The entire cabinet resigned and diplomatic relations were restored.

And I think it's Night Frost in Russian too, because it was Khrushchev who used the term.