In general, when looking for the cheapest flight to Oulu, try to choose a flight departing in February for the best deal.
In general, most flyers find the cheapest time to book a flight to Oulu is about 60 days prior.
In general, booking your departure to Oulu for a Thursday represents the best deal on airfare. Try to avoid a Saturday departure to stay away from the highest prices.
On average you can find the best deals on plane tickets to Oulu when looking for flights with evening departure times.