From what I see it's probably not winter (lack of snow), not autumn (lack of leaves on the ground). But that still leaves a pretty long time period with a bigger range of temperatures.
The vibrant leaves that you can see on trees in many of the pictures usually appear in mid-May and last until October, so that narrows it down in terms of temperature. Likely 15-25 C.
Depends on what you mean by 'short'. I think you're probably thinking of much further north in Norway. Summers in Oslo are usually from May or June to August. Sometimes there's 20+ C in March, sometimes it's 5 C in May. Night frost usually sets in around late October/early November, with snow usually arriving in November or December. Snow is usually gone by or during March.
Apparently the average temperature in 1890 was 1.3 C colder than it is now.
Well, that's fairly short by U.S. standards, at least when counting 20+ C weather, which in many states is nearly 6 months of the year, with summer heat lasting well through September in many places.
Even places south of Norway, like Netherlands, still considered pretty far north for many in the world, have relatively 'short' summers as well.
Ah, in that case then we have short summers. To me, "short summers" is the month or so of mosquito hell between spring and fall that they have in the northernmost parts of Norway.
That seems quite specific. How do you tell?
From what I see it's probably not winter (lack of snow), not autumn (lack of leaves on the ground). But that still leaves a pretty long time period with a bigger range of temperatures.