The region's lakes are surprisingly warm for the time of year, so warm that they're beginning to dry-up.

Outdoor swimming enthusiasts would usually have to wait a little longer for Oulu's various lakes to be warm enough to splash about in. But this summer's heat wave has led to them heating up incredibly quickly - sometimes by as much as 5 degrees a day.

Since a rather grey Midsummer, the heat has been on with such intensity that water levels are actually starting to decline. Many lakes in the Oulu region were between 17 and 22 degrees a few days ago, a well above average rise in their temperature. But the recent warm weather has also meant that water levels are between 5cm nd 35cm below average throughout the country, according to the Finnish Environment Institute.

Whereas areas in eastern Finland remain very wet, Oulu's water level, according to the institute, is 'much below the daily average', leading to it being marked in yellow on their map. Updated only today, Oulu's lakes are above 24 degrees, while some lakes in Lapland are still only eight degrees.

But environmental consequences aside, this is definitely the time to think about getting down to the local lake for a swim.