Whether you were house-sitting or in your own home, you’ve probably heard a creak or bump and immediately thought there was a serial killer inside with you. The good news is that’s highly unlikely, so what causes houses to creak?

While there could be some serious issues happening, house creaks are much more likely to be related to both weather and temperature.

When temperatures change in a house, a phenomenon known as thermal expansion and contraction happen. Warmer temperatures during the day can cause expansion, and then, when temperatures cool, you get contraction. The materials in a home—be they metal, wood, or something else—will all respond to those temperature changes resulting in those noises.

But it’s not just temperature. Weather also plays a role. Hot, dry weather can cause the soil under your home to contract and pull away from the foundation. As for rainy weather, the soil expands adding pressure. This is one noise you’ll want to keep your eye on, though, as damage could occur over time.

Finally, there’s settling. You’ve probably heard someone say a house “settles,” and this is actually true. Essentially, it means that the soil under a house has moved, and when that happens, the foundation sinks a bit. While this can be totally normal, if you hear the noises frequently and if they’re coupled with sticking doors, uneven floors, and floor cracking, you’ll want to bring in a professional to look at your foundation.

If you’ve ever run to the kitchen to grab a steak knife for protection while being home alone, don’t be quite so tense. House creaking is mostly normal, but you know, always lock your doors just in case.