Locals always know it is coming, but that does not stop the groans in the air.
MetService meteorologist Devlin Lyndon said the inversion would clear by the end of the week due to showers, but would likely be back for Saturday, Sunday and Monday.
An inversion layer is caused when two air temperatures meet and a pocket of air between does not allow for the cooler temperatures and moisture to be pushed further into the atmosphere and out of the Upper Clutha valley.
"Normally when you go up in the atmosphere, generally speaking the air gets cooler
"What happens at the boundary between the cooler air [and] warmer air [is] absolute stability."
This effectively acts as a barrier that stops the air mass ascending and getting out of the valley.
The moisture from the river and lakes has nowhere to go. Unfortunately for residents, each day the inversion layer stays the temperature drops.
The inversion layer sticks around in June because temperatures later in winter are more even, he said.
Mr Lyndon said there was "definitely more potential" for more of the gloom. But it will lift.
