I think there is such a thing as summer mania in Finland. Lidl even has an entire advertising campaign built around it. There are ads all over town right now saying things like "LIVE LIKE IT'S THE LAST DAY OF SUMMER" and "SUMMER COULD BE OVER TOMORROW". And the thing is...they're not wrong. Finnish summer is so notoriously short and unpredictable that this heat wave we're in right now - in the 20s C (70s and 80s F) - could be IT. This, right now in May, might be the only summer we get this year. Or not! But there's no way to know.
So summer mania manifests itself as people sunbathing everywhere, anywhere, at any time. You stay up late and wake up early, so as not to miss too much of the sun while it's shining. If the temperature is above 20C, a voice seems to say, GO OUTSIDE RIGHT NOW. If it gets above 25C, the voice adds, FIND A BODY OF WATER AND SWIM IN IT.
And you obey that voice, because summer could be over tomorrow.