Keeping the nursery on the cooler side at night is best for your baby.
While the exact number is debatable, keeping the room between 65 and 72 degrees at night is recommended. This will keep baby cool enough to sleep well without being cold.
You can dress them in a set of footed pajamas and use a light sleep sack if necessary. In general, babies only need one light layer more than adults to keep warm.
Keeping a baby too warm is dangerous because little ones cannot regulate their body temperatures by sweating like older children and adults, meaning they can get overheated easily.
And finally, never leave loose blankets in the crib because they increase the risk of suffocation.