Over the 4th of July holiday, the weather station at LeConte Lodge registered an over-night low of 38º. But the climate data for that time of year at that elevation says the lows are only supposed to be in the low 50's.
That's why I added the note that temperatures can be +/-15º from the seasonable average temperatures.
So based on seasonable averages of a highs of about 60º in the valleys and 25º on the summits, temperatures around Thanksgiving can be as high as 75º down in Cades Cove, and as cold as 10º at Tricorner Knob Shelter.
When you throw in the possibility of Snow, you quickly understand RED-DOG's suggestion of being prepared for all weather conditions.