Delaware Water Gap National Recreation Area - PLAN YOUR VISIT: Things to Know (U.S. National Park Service)

SPRING
ϑ Climate is variable. Temperature can drop rapidly after sunset on warm days.
ϑ Ice in the deep ravines can last until May, and some roads such as Dingmans Falls may stay closed until the ice is gone.
ϑ The temperature of river water is colder than air temperature, and can bring on hypothermia (a critical loss of body heat.) It is not advisable to go canoeing until the sum of water and air temperatures is at least 100 degrees. Bring warmer clothing to go out on the river. Swimming is not advisable. Wetsuits may be required for river use.

SUMMER
ϑ Air temperatures average from 75 to 85 degrees F, with some days in the 90s, and with lows to the 50s. There may be some very hot and muggy days in summer, but generally the heat and humidity are far more comfortable than in the cities.
ϑ Thunderstorms along the river can be violent—everyone on and in the river should head to shore when storm clouds form. Water temperatures from May to September rise from the mid-50s to the mid-70s in July. Weather is cooler on the river.
ϑ Hikers should remember that even in the long days of summer the light fails early in the ravines—in all seasons, be off the trails two hours before actual sunset times when hiking ravines or spurs to the Appalachian Trail.

FALL
ϑ Climate is variable. Temperature can drop rapidly after sunset on warm days.
ϑ Mixed forests and harvested fields offer beautiful strolls in the woods and picturesque rural landscapes for windshield tours. Millbrook Days, on the first weekend that falls fully in October, often enjoys some of the most beautiful weather in the valley all year.
ϑ Fall colors make the Gap especially photogenic, but winds in the Gap can be strong. In late fall, some of the best vistas along the hiking trails will emerge when the leaves are down.
ϑ The road to Dingmans Falls will probably close with the first snowfall and remain closed until late spring.

WINTER
ϑ Air temperatures from December to March are frequently below freezing, with numerous snow and ice storms in some years, and little snow in other years. Water temperatures drop from the 50s to the 30s by December, with most of the river usually freezing over each winter.
ϑ The river can freeze over completely or partially, but it is NEVER safe to walk out on its surface; leave ice fishing to the local residents who know the way to go about it.
ϑ Icy roads and fog are always possible. River Road in Pennsylvania and Old Mine Road in New Jersey may close intermittently due to ice. Other roads in the park may be gated closed.
ϑ Due to cold and limited sunlight, hikers should be off the trails by 2:00 PM.