Do your windows have drafts? Here’s one way to tackle the problem.
You can buy a window insulation kit for $15 to $25 online or at your local hardware store. It should come with double-sided tape and plastic film for covering the inside of your windows.
1) Clean the window frame with a damp cloth or rubbing alcohol.
2) Apply one layer of double-sided tape to the window frame and remove the back cover.
3) Unfold the plastic film that comes with the insulation kit. Adhere the plastic film to the tape starting at the top, move to the bottom, and then finish at the left and right sides.
4) Grab a hair dryer. Use it to shrink the film to provide a better seal around the window, and to work out wrinkles. The heat will seal the plastic and window together. Most insulation kits have multiple sheets of plastic, so you should be able to repeat the process for other windows.
Optional: For extra insulation, place bubble wrap over the window, as a first layer, and then put the plastic sheet over that. Use packing tape to connect different pieces of bubble wrap.