But I'm not going outside

A few weeks ago I told Graeme to put on his pajamas. We give him almost total free reign over what he wears. He came back with short pajamas on a frigid day.

Me: Graeme, it's too cold for short pajamas. You need warmer ones.

G: But I'm not going outside.

What could I say, so I let him wear what he chose. And prepped myself for his icy feet climbing against my legs when he climbed in bed about 2AM, which he did.