Ravenna is just a little inland from the sea (the Lido di Ravenna is about ten minutes away). I've been there in the heat of summer and it's fine. Some of the major streets have arcades similar to Bologna (but not as extensive). I love Ravenna, go back at least every other year. I like to stay at Hotel Byron Carlysle (or Carlysle Byron?), which is next door to an excellent restaurant, La Bella Venezia.
Ferrara would be another good place. In addition to the Castello, Duomo and major museum, there are lovely walks away from the Centro Storico to other sights. The charming Hotel Corte Estense is off the main street of the Centro Storico, has a small courtyard, and the staff is very helpful. An excellent restaurant with typical regional dishes is Cusina e Butega, on the main street around the corner from Hotel Corte Estense.
Both of these cities are well known to tourists, but manage to maintain their integrity as places where people live and work.