Sudden house fly infestation — where do they come from so fast?

Hi everyone,
I’m honestly confused and a bit grossed out. A few days ago, there were zero flies in my house, and now it feels like they appeared overnight. I’m seeing them mostly in the kitchen and near windows, even though we’ve been keeping things pretty clean.

No food left out, trash goes out regularly, and nothing obvious smells off. That’s what’s throwing me — how do house flies multiply this fast, and where do they usually come from when it seems so sudden?

Trying to figure out if I’m missing something obvious or if this just happens sometimes.

House flies lay eggs incredibly fast. If there’s any hidden source, you can go from none to dozens in a couple of days.

I once found a dead mouse behind a storage shelf and that explained everything. Not saying that’s your case, but hidden stuff matters.

Warm weather plus open windows is usually all it takes. They’re way better at finding entry points than we think.

People assume flies mean a dirty house, but that’s not always true. Sometimes it’s just timing and temperature.

@QuietHome88 If you’re in an apartment or townhouse, they might not be your flies at all. Shared walls make things tricky.

If trash pickup was delayed or bins sat outside longer than usual, flies could’ve bred there and followed the smell inside.

Late summer is prime time for this. Happens to me every year for about two weeks, then disappears.

I once found a dead mouse behind a storage shelf and that explained everything. Not saying that’s your case, but hidden stuff matters.

@BasementSurprises Good point, also check under appliances. Old crumbs and moisture can hide there forever.

I’d focus on finding the source instead of swatting. Once the breeding spot is gone, the problem usually stops on its own.