If you’re planning to be in Finland in late June, you may need to tweak your itinerary.
Almost every museum I checked in and around Turku and Tampere is closed Friday, June 23, through Sunday, June 25. Most museums are closed on Mondays, so that means four days in a row with limited indoor sightseeing options. I knew Midsummer was a serious thing in the north, but I had no clue it was that big a deal in Finland; holiday lists I found online listed Midsummer Eve and Midsummer Day but did not include Midsummer Sunday. A lot of the museums also close a few hours early on June 22. Although I spend a lot of time walking around interesting neighborhoods, I don't like being limited to outdoor activities for 3 or 4 days in a row. Finland can be very rainy.
The long holiday weekend has caused me to take a closer look at some attractive small towns with no must-visit indoor attractions. Of course, it’s impossible to find a decent-quality, reasonably priced hotel room in a coastal town over Midsummer weekend at this point, so I had to compromise. This is what I’ve ended up with:
June 21: Arrive Turku (3 nights) on overnight ferry from Stockholm. See Naantali and Pargas.
June 24: Train to Ekenas/Taamisaari (2 nights). See Hanko.
June 26: Train to Helsinki (4 nights).
June 30: Train to Tampere (4 nights?). See museums in Iittala, Saaksmaki and Hameenlinna. It may make more sense to split nights between Hameenlinna and Tampere.
July 4: Back to Helsinki for a few days, then on to Tallinn. (I cannot predict in advance how many nights I need in total for Helsinki. This lets me pre-book the initial stay.)
If anyone else is going to be in Turku, Tampere or Helsinki over the critical weekend, I’ll be glad to post the information I’ve gathered on the museums’ holiday closings. Although many websites have exceptional closures listed, not all do, so I’ve contacted some of the museums to get that information.
Preliminary research indicates Helsinki doesn't shut down for quite as long or as completely as Turku and Tampere, but options will still be a lot more limited than usual in the capital.
Edited to add: I forgot to mention that Finland has a country-wide Museum Card good for a year. The current cost is €76. For anyone covering multiple cities in Finland who enjoys museums (there are a lot of art museums in the country), the card may be a significant money-saver. It doesn't cover every museum, but it seems to cover the vast majority of them.
There's also a Helsinki card, but I haven't dug into the details on that.