Two of my dcks would show up in only sweaters in the winter all the time. Parents chose to leave their snow suits here at dc even though I insisted a couple of times that they may want to put them in their jackets at least....they always said "it's just in and out of the car to the house" so I never forced the issue even though it irked me! They still leave their snowsuits here for when we go out to the parks, but if they didnt and continued to just bring them in sweaters I would definitely ask that they either dress them appropriately for the weather, or leave warmer attire at dc for outings.