skimmer overflowing at night

i recently installed a new dc octopus diablo 170-int skimmer and has been running great for the last 4 months but all of the sudden at night it fills up my collection container because it goes crazy. I currently have a 30 ft 3/4 line running outside for fresh air to skimmer muffler and the only thing i can think of is that the air is starting to get cold here at night but could that cause it to do this? If i leave the air line off the muffler it runs fine i dont get it.