Littleton rewards visitors in every season, though each comes with different priorities.
Summer (June–August) is peak hiking season. Trails in the White Mountains are clear, Franconia Notch is at its most accessible, and the town fills with through-hikers on the Appalachian Trail as well as White Mountain day-trippers. June is particularly special if you make it to nearby Sugar Hill, where the roadsides erupt in purple and pink lupine — a relatively brief window, usually the second and third weeks of June.
Autumn (mid-September to mid-October) is the most popular time, and for good reason. The foliage in northern New Hampshire is among the finest in New England, and the mountains behind town turn spectacular shades of red, orange, and gold. Peak colour around Littleton typically falls in the first two weeks of October, and weekends can be busy on the Kancamagus Highway and Franconia Notch. Book accommodation well ahead.
Winter (December–March) brings skiing. Cannon Mountain in Franconia Notch is the closest major ski area, and the town is quiet enough that you'll have a much more local experience than in ski-resort towns. The Pollyanna Glad Day festival takes place in June.
Spring (April–May) is mud season — trail conditions can be poor and the mountains are often still snowy above 4,000 feet. It's the least visited time, though prices are low and the waterfalls on the Flume Gorge trail are at their most powerful.