hard to tell much in the way of details from your picture. Is that haze condensation? If so is it inside, outside, or between double panes of glass?
I am going to assume since you said apartment that you rent and do not own, so that 1)you do not want to invest significant time and money doing major repairs and insulation upgrades and 2) even if so inclined you would not be allowed to undertake significant work.
I use a product call seal n peel (
http://www.homedepot.com/p/DAP-Seal-N-Peel-10-1-oz-Removable-Weatherstrip-Caulk-18351/100140056) to seal some air leaks seasonally. (no a/c so air leaks in the summer are not a big deal especially as the windows are frequently open). It is essentially caulk that you can peel up at the end of the season, but it might get difficult to remove after a year or so.
A properly sized heavy material curtain/blind would also be an option, in colder climates they even market some as "thermal curtains".
Have you determined where exactly the air is finding its way through? It may be possible to rehabilitate or replace the weather stripping if that is the issue.