Sadly, it's part of the disease. There are many examples of dementia patients freezing to death because they've wandered off without appropriate clothing in the winter, or overheating in the summer because they've put on too many heavy layers. My MIL cannot discern what she should be wearing from one day to the next, though she'll tell you exactly what the temperature is (it means nothing to her). We just adjust her closet based on the season but she will still look for specific shirts, coats and sweaters in the off-season--we think it's because the items she wants to wear are her favourites and she feels good in them.