The average daily maximum temperature in Tampere is 22 C in July and 20 C in June and August. The leaves turn yellow in the latter half of September, red in the first half of October and fall in the second half of October. Persistent snow cover usually lasts from early December to early April. So, we have four months of snow. That's about the same time there are fully grown and green leaves on the trees.
Leaves never fall in August except for the far north about 1000 km further to the north than the south where nearly all the biggest cities are.