4) WEATHER...the summer heat is gone, but the need for a heavy coat is typically not necessary. The perfect temps for travel and ideal for sight seeing!
3) COLORS...the Fall season is full of changing colors everywhere from the NYC to California in the US and Tuscany, Italy to the English countryside in Europe. TIP: For visiting Canada in the Fall, the colors peak earlier than most places in late Sept/early Oct.
2) LESS CROWDED...sight seeing is SO much more enjoyable with less people! The lines are shorter and the most popular attractions are not as crowded = a more pleasant experience!
1) AND THE #1 REASON (NO SURPRISE) IS LESS MONEY! The Fall is called the "Shoulder Season" and comes with a savings for you! Everything from airlines running deals, hotels running promotions and B&Bs are more negotiable.