We are in our last full day of a week in Florence and I thought I would share a few thoughts:
Yes its hot and crowded in the summer, but if you can only go then, I would rather be hot in Florence than cool in a lot of other places! As long as you plan carefully in advance for museum visits, you can avoid the crowds. Find streets and restaurants that are off the beaten path and you can still feel the charm and be relaxed. For the heat, I recommend a cooling towel. They REALLY help. Look it up and buy one!
We stayed in St. Ambroggio area and it was great. A real neighborhood with locals and ex-pats. The market itself is fantastic. Cheap amazing produce and other goods. There are really nice restaurants with locals and some great cafes for morning coffee and pastries. It feels a bit like you are living here rather than being on vacation.
If you are coming in the near future, book a visit to the Brancacci chapel. It is under construction for about a year so it is closed. But the 18th of each month they open up tickets on the website for the next month. You get 30 minutes with a small group and a guide to climb up into the scaffolding and look at the frescoes at eye level. You can also book a short guided tour in English. It is fantastic and a once in a lifetime experience.
Two recommendations of more private experiences that we splurged on a bit. We booked a guided walk and Accademia tour with https://expertflorenceguide.com/florence-private-guide/ and she was great, we really enjoyed our time with her and felt it was well worth it. We also did a tour with https://www.fiesolebike.it and loved it.
No, stopping for two gelatos a day is not gluttony!