The USA is the fourth-largest nation on earth with a total area of 9,629,091 sq km and sprawls across six time zones from west to east. Having such an immense geographical spread incorporating multiple time zones, you get to experience a variance in climate which can get extreme at time, as you move from one state to another. Hence, it’d be quite misleading to make recommendations on the ‘best time of the year to visit USA’. Talking about climatic or weather variations, you could be sweltering in the suffocating Las Vegas heat during daytime in June or July and when you reach Mojave, a few hours of drive from Sin City, in the evening you could be literally shivering.
Or, if you make it to the top of Grand Canyon early morn, you’ll feel the nip in the air but when you hike down to the bottom, the temperature could be something like forty degrees. The entire North US experiences a somewhat similar climate from one coast to another with minimal weather fluctuations. Snowfall and snowstorms are quite heavy during the long winter when almost everything is covered in a thick blanket of snow. The protracted winter pushes the spring season to May when flora and fauna appear colorful and bright.
Summers in the North vary from being pleasantly warm to stiflingly hot and vapid and you might prefer to spend more time in the beaches and national parks where the weather is definitely cooler. You’ll definitely be thrilled at the rapidly changing hues of the sky and the earth during autumn. So visiting the Northern states is ideal during early summer, spring, and autumn.
Seasonal changes are less defined in the Southern US though the differences could become marked as you move from Florida to Texas and further on to Colorado, Kansas, and Oklahoma. Summers are hot and tepid while winters are warm and dry. Visit the South either in autumn or spring but be prepared to run into hurricanes.