Snow frequently blankets and park and preserve in winter months, though the dunes tend to melt off within a day or two. NPS/Patrick Myers. Snow falls about once per week in winter months. NPS/Patrick Myers. December. December brings heavier and longer-lasting snow along with much colder temperatures. The average high is 36 F with lows around 11 F, but sub-zero temperatures are possible. Snow falls about once per week on the dunes and mountains. Roads are usually quickly cleared of snow.