Multiple school districts and colleges in Houston were closed Monday in response to a city-wide boil water notice after a power outage at a purification plant.

Why it matters: The city's more than 2 million residents are under the advisory, which means water for drinking, cooking, washing hands and faces and brushing teeth should be boiled for at least two minutes.

What they're saying: Houston Mayor Sylvester Turner said on social media early Monday that the city believes the water is safe but was required to issue the notice after the drop in water pressure at the plant, which serves approximately 2.2 million customers daily.

• Turner said water sampling done by the Texas Commission on Environmental Quality would begin on Monday and that the notice could be lifted 24 hours after the city is told the water is safe.
• "The earliest would be tomorrow night or very early Tuesday morning," he said.

The big picture: The closed school districts and colleges included Houston Independent School District (ISD), Aldine ISD, Pasadena ISD, Spring Branch ISD, Houston Community College and Lone Star College - Greenspoint and Victory.

• Houston ISD is one of the largest school districts in the U.S.

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