Cold air sneaking around a window usually comes from one of two places, and they take different fixes. Failed caulk is on the outside — the bead between frame and wall cracks and peels, letting air (and water) in. Scrape it out and re-bead with exterior-grade caulk.
A draft that moves when you push the sash is weatherstripping — the compressible seal between the moving parts. Worn foam or felt gets replaced in strips; it compresses flat over the years and stops sealing long before it looks bad.
The quick test: on a windy day, move a lit incense stick slowly around the frame. The smoke tells you exactly where the leak is before you buy anything. If the frame itself is rotted at the sill, sealing won’t hold — that’s a repair first, seal second. CMG Bridge serves Staten Island; call-outs Monday to Saturday, $125 for the first hour.