Summer temperatures in southern Sweden are comparable to Blighty - even extending to the legendary heatwave we shared in 1976 . But even there the warm season is short: right now there could still be snow and frost, and that frost may return by early September. But in northern Sweden, anything into double digits is a warm summer day. And the summer is of course even shorter. They don't call the ground there "permafrost" for nothing.
 In 1976, even our local (Småland, southern Sweden) lake reached 28 degrees at the surface, though swimming down was refreshingly much colder. That's the only time I've known it to peak above 22.
 Last time I was there in early May, for my granny's 90th birthday, daytime peak temperatures were around 3 degrees.