In general, when booking your flight to Helsinki, November is the cheapest month on average.
In general, most flyers find the cheapest time to book a flight to Helsinki is about 60 days prior.
On average, the cheapest flights to Helsinki are found when departing on a Tuesday. Try to avoid departing on a Saturday, as this is usually the most expensive day.
On average you can find the best deals on plane tickets to Helsinki when looking for flights with morning departure times.