The United States has varied weather conditions, and the best time to visit depends both upon the location and the season. Spring (March- May) and autumn (September-November) are generally cooler, more comfortable times to visit. The summer months (June-August) are generally hot regardless of the region, but winter temperatures (December-February) can vary substantially depending upon the part of the US you are visiting.

The southern part of the country tends to be warmer than the north. The general climate of the continental US is temperate, but keep in mind that Hawaii is tropical and Alaska is arctic. Many of the country's dependent territories, such as Guam, Puerto Rico, and the US Virgin Islands, are also tropical.

Summer is considered the peak tourist season throughout the country; other popular travel times are major American holidays, especially Thanksgiving and Christmas, as well as Easter Week and the school holiday known as Spring Break. Certain destinations, such as New York, are perennial favourites and are busy year-round; even when the weather may not be pleasant, these destinations have particular attractions or experiences that always draw travellers.

In some parts of the country, travel services may be limited during the low or off-season, largely due to weather conditions.

As the US is a vast country with varying climates and four distinct seasons, packing clothing that allows you to layer for warmer and cooler conditions is recommended, especially if you plan to travel to different regions of the country. What you pack will largely depend upon the kinds of activities you plan to enjoy. Outdoor-lovers will need clothing and shoes that are appropriate for the terrain and the activities they have planned; visitors to cities will need a range of casual outfits and perhaps one smarter outfit for a night of fine dining or theatre.