Bed bugs are generally the most active at night when you are sleeping. This is their optimal time to feed on you undetected.  Research has shown that bed bugs tend to come out between the hours of 3 a.m. and 5 a.m., which is when you are in your deepest sleep.  When you are in a deep sleep, you emit carbon dioxide as you breathe. Bed bugs are very attracted to carbon dioxide and it serves as a signal for them to come out and feed.Although bed bugs are active year-round, they tend to become more active in warmer weather or in warm climates, although cold weather climates such as Alaska are also dealing with bed bug infestations.