Winter conditions on the South Rim can be extreme. Be prepared for snow, icy roads and trails, and possible road closures. Winter weather typically begins by November and becomes well entrenched by December and January, with frequent light to moderate snows and increasingly colder weather. Low temperatures are generally in the teens along the Rim; however afternoon high temperatures still average in the 40s (4-9°C), due to the amount of sunshine the area receives.

Along the river, cold air typically becomes trapped in the canyon leading to high temperatures only in the 40s and 50s (4-15°C) and low temperatures in the 30s and 40s (-1C-+9°C). Even with all of the winter sunshine, significant snowfall can be expected during the winter with an average snowfall of 50 to over 100 inches (1.3-2.5m) per year on the Rim, and occasionally snow will make it even to the river.

Between storms, when dry high pressure builds in, winds become light, and fresh snow cover is on the ground, minimum temperatures can plummet, especially on the Rim, with sub-zero temperatures likely. Snow continues to be possible at the higher elevations through April. During the winter and early spring months, fog occasionally forms due to radiational cooling from snow cover on the ground. However, this fog usually breaks up quickly by morning.

<a href="http://www.nps.gov/grca/planyourvisit/weather-condition.htm" rel="nofollow">www.nps.gov/grca/planyourvisit/weather-condition.htm</a>