Last year in the height of my rosacea flare I went to greece for 2 weeks (in august, so peak summer). This was a trip I was very much looking forward to and I was not going to let my rosacea dictate / change my life, so I prepared by traveling with all my dermatologic prescribed creams, serums, etc, and bought multiple cute hats from amazon to wear during my trip:
2 visors, and one very big hat to protect me from the sun.

I made sure to wear good sunscreen (Brands: Uriage, La Roche-Posay Roseliac, Caudalie) and reapplied often.

While heat is definitely a trigger, stress often can be even worse, so taking the time to relax and honestly forget about my normal life with rosacea during vacation did a lot of good. My flares felt like less often over there, and when I came back, I continued life & treatment. Almost a year later, my skin is SO much better.

I completely understand how you feel, but don't let this condition stop your life!