Thanks for reading my posts, and I would add some pertinent observations...
Not all of the nine islands compare with hydrangea blossoms. For me, the top choices would be Sao Miguel, Terceira, Faial, and Flores. The others have lots of them, but not as spectacular.
The more southern the islands, generally the earlier the blooming season. However, weather can play an important roll depending on rainfall, either too much or too little. After the first half of June has better odds, as Balso pointed out.
It can be humid any time of the year. The summer days and nights can certainly have warm, moist air. Nights without an air conditioner makes for restless sleep. June and July have been equal on my many visits.
The festas (feasts) are best in July and August, but it depends on which islands. Terceira in June, with Sanjoaninas, is phenomenal.
The Azores are continually getting more popular with tourism. Make it a point to make reservations at anywhere that accepts them, including restaurants. I have made reservations many months ahead of time for places I really wanted to visit. The thermal baths in Sao Miguel (Poca da Dona Beija and Caldeira Velha) are a couple of examples that now require them. So are the lava tubes on Pico (Gruta das Torres-currently closed) and Sao Miguel (Gruta do Carvao). Algar do Carvao in Terceira will not reopen until mid 2026...hopefully. Museums never need reservations and are seldom busy. For dinner reservations, especially restaurants on the islands of Sao Miguel, Pico, and Terceira, an email or phone call a week or two before visiting is suggested. I have scrambled for places to eat dinner many times in Ponta Delgada, since normally we are a very big group. For the smaller islands, a couple of days beforehand should suffice. I have never made lunch reservations on any island.
