Despite a freezing day under the inversion layer of cloud today (Monday May 20), the MetService has predicted the skies will clear up as the week progresses.

The inversion is an annual weather event which results from rapid cooling at ground level under clear sky conditions. The cloud is formed at low levels due to the temperature difference of the air just above the surface of the land and the air higher up.

Last year the inversion stuck around for a miserable few weeks, but MetService meteorologist John Law told the Wānaka App there is “much more active weather” over the country this week which should provide enough wind to move the fog.

“You shouldn’t have the long, lingering cloud,” he said.

“We’ve got the chance of a cloudier morning on Tuesday, but on Wednesday and Thursday the skies should be clearer,” he said.

The plus side of the cloud, he said, was it “acts as a bit of a blanket”, which means temperatures should be warmer than those last week.

The MetService says the lack of heating at this time of the year, when the sun’s at its weakest, combined with a lack of wind to mix dry air from above, means the moisture stays in basins and valleys.

Usually under a ridge of high pressure there are light winds and generally clear skies, which allows rapid cooling to take place at the surface, but if there’s moisture trapped at low levels that condenses into fog, which can stay trapped in these valleys for days.