Here are my top five recommendations for daytrips in winter. All are in An Hour From Paris except for Malmaison, which is in Half An Hour From Paris.
The short walk through the forest to the Musée de la Renaissance in the château is particularly magical in the snow, which doesn’t melt as quickly as it does in Paris.
Conflans Ste Honorine
La Goèlette island restaurant at Andrésy is reached by speedboat. Optional short riverside walk to the station at Conflans Ste Honorine.
Watch or join the dancers at the Guinguette Auvergnate riverside restaurant. Optional short riverside walk to the station at Choisy-le-Roi.
Visit the Villa Savoye built by Le Corbusier in 1929. Optional short riverside walk to the station at Villennes sur Seine.
Visit the home of Napoleon and Josephine, perhaps followed by lunch at the nearby Brasserie du Château.