Mt Hutt in Canterbury will also be closed today and The Remarkables is only open on weekends.
Coronet Peak is the only Queenstown NZSki area open on weekdays, with the company having scaled back operations already because of Covid-19 border restrictions.
The ski area normally plays host to night ski on Wednesdays, with lifts running until nearly 9pm.
A NZSki media spokeswoman said the short notice of the move to alert level 2 meant it was the "responsible thing to do".
"Before the season started we worked with other ski areas to develop alert level 2 protocols for the industry which allow us to operate.
"So we are prepared but are taking the day to ensure we have all of the protocols in place and to give us time to communicate to our guests about what they can expect on our mountains at level 2.
A statement on Cardrona Alpine Resort's Facebook said: "Treble Cone and Cardrona will be closed on Wednesday August 12th while we coordinate our response to a level 2 environment. We will update you with more information during the day tomorrow."
Porters Alpine Resort is open but has contact tracing measures in place.
