This is the 315th most frequent Finnish word.
helmikuussa
"In February."
Here, 'helmikuussa' indicates the time frame (February) during which a generic condition (cold and snowy weather) occurs.
Helmikuussa on usein kylmää ja lumista.
In February, it is often cold and snowy.
'Helmikuussa' specifies when the action of traveling to Lapland took place.
Matkustimme Lappiin helmikuussa.
We traveled to Lapland in February.
In this sentence, 'helmikuussa' is used to denote the time period (February) in which an event (holding of winter sports events) occurs.