Cloudy water, also known as white water, is caused by air bubbles in the water. It is completely harmless. It usually happens when it is very cold outside because the solubility of air in water increases as water pressure increases and/or water temperature decreases.
When water flows from your tap, tiny bubbles from dissolved air can be released and make your tap water appear cloudy. This problem is more frequent in winter, as cold water holds air longer than warm water. Cloudiness caused by air bubbles does not pose a health concern, but for some people it is unappealing. After a few minutes, these air bubbles disappear from a standing glass, so a good solution to this problem is to keep a jug of tap water in the fridge for drinking.
In the winter, water travels from the reservoir which is very cold and warms up during its travel to your tap. The air that is present is no longer soluble, and comes out of solution.
In addition, once water from our reservoir enters the transmission and distribution pipes, the water is pressurized. Water under pressure holds more air than water that is not pressurized.
Once the water comes out of your tap, the water is no longer under pressure and the air comes out of solution as bubbles (similar to a carbonated soft drink). The best thing to do is let it sit in an open container until the bubbles naturally disappear.