Tom :- the holiday weekend mentioned by Janko is the religious weekend of Ascension Day. About half of Europe has that five-day-weekend off work.
Practically speaking, there is a choice between "the first three weeks of May plus first half of June" and "late Summer"?? This comes about because we are a bit late for April now and most family holidays seem to occur during July or August, of course they would generally have priority for most people.
So . . . Spring ??? Or late Summer ???
Locations outside of the EU might be a little far away, in travel time or costs. I have not found the Arles opening week to be expensive (but I do stay in a tent for that) provided that one doesn't try to book the TGV very late. If we are going to be silly, lets go to Kabul - at least it will be safer this year than in 2015 . . .
Later in the year could suit the Northern Baltic locations very well, if we wish to have fine weather. Earlier might be good for more central locations, such as Brussels and/or Antwerp, Bruges etc. Gdansk also looks to have reasonable average
weather in May or June. Romania or Hungary can be interesting too. Cheap airlines are useful, as are the train networks and of course self-drive for the people nearest to a location.
If we can find a vague consensus, or top-five, I'll make a poll thing like last time.
