Bad smelling cold water

Last saturday our cold water started having a stong odor...almost like a litter box. The hot water, on the other hand, doesn't smell. The smell is overwhelming but we can't figure out what is causing it. It's coming from every faucet in the house. Even the toilets smell. I know hot water sometimes has a sulfery smell...but what can be causing my cold water to have such an overpoweringly foul odor?? Help!

You don't say whether you have your own well or if it's city water??

I've got city water

In that case, I'd call your city. Our city has various tests / treatments of our local holding tanks and wells that sometimes cause color or odor issues. I have always gotten an acceptable answers (and sometimes they have had me bring in a water sample for testing) when I call. I think I've called about 3 times in 12 years