Have you ever heard booms on the roof of your house? I have posted my experience before on this blog. It happened in 1994. This was in the middle of the winter and it was well below freezing:

It had snowed a lot, and we had removed the snow from our roof. In the evening, while in bed but not asleep yet, we heard a sudden, very loud but soft impact on the roof (our bedroom is under the roof). It was really loud and it startled us. It happened two more times that evening, and one time at six o’clock in the morning. We could not find any reasonable explanation for it. The closest thing I could compare it to, was that a big ball of snow had fallen on the roof from very high up. In the morning I checked the roof but there was no trace of anything.

This was a one time occurrence. It never happened again. This excludes that it has anything to do with the house expanding or contracting because of the temperature. I never figured out what it might have been. Recently I found a Reddit post of someone who had this happen to their roof too:

Earlier this week, I heard a loud bang, and it was strong enough to shake my new house. My first instinct was that someone kicked in my door. When I saw that wasn't the case, I checked my roof, and nothing. No one else outside checking. Now, I live near a military base, so, my first thought was some kind of artillery. It was around 515pm.

Tonight, I heard another, just as loud, and the whole house shook. It was about 11pm. I immediately noticed that I didn't hear a boom outside the house. I realized I was right, that it sounded like it came from the roof/attic. Maybe a minute later, I heard another bang, like something was dropped, maybe. It didn't shake the whole house this time, but it was similar, just not nearly as big.

I've been watching a lot of weird YouTube videos for a while, so I checked my attic to see if there were signs of a person up there. But I didn't see anything. I stuck around to listen for animal rustling or something, but there was nothing. Now, my wife doesn't really leave the house, and she's a light sleeper. Plus, I have a big dog that would notice if someone was sneaking into and out of our attic. I can't think of anything tangible, I'm hoping maybe someone knows of something, as I am a new, first time homeowner. Please tell me I just walked around my house twice with a knife for no reason. Something as simple as artillery that you don't necessarily hear from a couple miles away, but has a huge shock-wave, or some part of my house needs a repair or something.

I found another account:

My children and I are visiting my parents for the month.
All of us were sitting in a room together, watching TV, and we heard it for the first time at 11:15 am. BOOM. We thought first maybe a frozen tree branch fell on the roof. (we have two large trees in the front yard, and we had the arctic blast come through and everything) no branches fell. Our dog wasn't alarmed, so we forgot about it. 20 or so seconds later BOOM. It was louder!
We went around the house and turned everything off so we could listen to see where it was coming from. Another 20-30 seconds later. A louder BOOM and we could feel the house shake! We figured out it was coming from the "sun" room, the room that has the door to the backyard and it has a skylight. It also had the stairs leading up to the 2nd story that was built after the original construction of the house. The first story has 2 separate sections of attic, one with the heater unit, the other is empty, just storage. The empty attic was the one making noise.
There had been about 5 or 6 booms, and they were SO loud at this point, we thought the house was going to explode. I called the fire dept and we all ran outside. Our neighbors came out and let us come in their house. They told us they could hear the booms from inside their house! Sure enough, we waited and were real quiet, and we could hear the booms a few times before the fire dept. came. I know they heard it too because it happens while they were inside. We waited and waited for them to come get us.
Finally they came and got us but they said that they turned off the heat and checked up in the attic and they couldn't figure out what the hell it was!
there hasn't been a noise since then, but it's midnight and I woke up panicked like it's going to happen again and it was the scariest thing that's ever happened to me. I have an infant and toddler and were all sleeping in the "built on" second story! (Yahoo Answers)

Scientists are quick to point out that the loud booms are caused by ice or frost quakes. Frost quakes are caused by a sudden rapid freezing of ground and bedrock, usually when temperatures go from above freezing to below zero. As moisture absorbed in the rock and soil freezes, it expands. This puts a great amount of stress on the areas around it. Eventually, the stress is too much and the soil and rock will crack in an "explosive" manner, creating a loud sound and even shaking the ground surface. Yes, people hear them once in a while, but these are sounds coming from the ground. In my experience and that of the other person above, the sound came from the roof as if something hit it.