By region

Northeast and Midwest cities: May to June and September to October. New England foliage: late September to mid-October.

The South: March to May and October to November; summer is hot and humid. New Orleans is best February to May (Mardi Gras through Jazz Fest).

The Southwest deserts and canyon parks: March to May and September to November; summer exceeds 40 C. Florida: December to April (dry season); summer is hurricane season.

The Rockies: July to September for hiking, December to March for skiing. Hawaii: year-round, driest April to October. Alaska: June to August.

Crowds and prices

Summer (June to August) is peak everywhere: book national-park lodging a year ahead. Thanksgiving week and the Christmas to New Year stretch are the most expensive travel periods in the country.

Shoulder seasons (April to May, September to October) bring the best combination of weather, prices and availability in most regions.