when it is that cold, they are usually not interested in food anyway. wait for a warmer day.
i put my dry sugar on the inner cover. some put it on newspaper. you can put a couple of small slit in th paper so that they don't have to go so far to access.
if you are in a dry area, moisten the sugar with a few sprays of water. one of the reasons i use the inner cover is that my area is so wet, the sugar helps absorb some of the moisture. it helps keep moisture that blows in sideways from pooling and dripping from the inner cover. for you, you may need to dampen the sugar in order for them to use it, and sugar inside my be a benefit to you in absorbing moisture inside.