Air pollution levels in the Central Otago town of Alexandra have risen to double the level permitted by national air quality standards for the second time this year.
Otago Regional Council says pollution reached its highest level for the year in the town on Sunday.
It says people should still use woodburners to keep warm but is asking them to avoid damping down fires overnight because that creates large amounts of smoke without providing much warmth.
The council also wants people to swap older woodburners for more modern and efficient designs.