ChatGPT's ideas:

U.S.-Based Cooler Places

Alaska
Avg. highs: 50s–60s °F (10–18 °C)
Glaciers, wildlife, fjords; ideal for cruises or Denali NP adventures

Pacific Northwest (Seattle, Olympic NP, Oregon Coast)
Avg. highs: 60s–70s °F (15–25 °C)
Lush green forests, mountain ranges, and cooler coastlines

Northern Michigan / Upper Peninsula
Avg. highs: 70s °F (20–25 °C)
Great Lakes, charming small towns, and pine forests

Maine (Acadia National Park, Bar Harbor)
Avg. highs: 70s °F (20–25 °C)
Ocean breezes, seafood, and beautiful coastal hikes

Montana or Wyoming (Glacier or Yellowstone NP)
Cool mornings/evenings, warm but dry days
Wild landscapes with abundant wildlife and fewer people

International Cooler Destinations

Iceland
Avg. July highs: 50s–60s °F (10–16 °C)
Volcanoes, waterfalls, black sand beaches, and 24-hour daylight
Great for hiking, road trips, and natural hot springs

Canadian Rockies (Banff, Jasper, Lake Louise)
Avg. highs: 60s–70s °F (15–25 °C)
Glacial lakes, snow-capped peaks, and wildlife
Ideal for nature lovers and photographers

Norwegian Fjords (Bergen, Geiranger, Flam)
Avg. highs: 60s °F (15–20 °C)
Majestic fjords, cruises, and charming Scandinavian towns

Scotland (Highlands, Isle of Skye)
Avg. highs: 50s–60s °F (10–18 °C)
Castles, lochs, dramatic coastal cliffs, and minimal crowds

New Zealand (South Island – Queenstown, Wanaka)
It’s winter in July!
Skiing, hot springs, and alpine lakes