Perth weather: Foggy morning caused by by cold, clear nights

A cooler overnight temperature with little to no cloud meant Perth woke to a foggy morning on Thursday.

A cold front passed through the city last weekend and earlier this week, contributing to not only chilly mornings but a thick blanket of fog that covered the skyline.

Perth Airport confirmed that some flights had to be diverted because of the conditions.

Bureau of Meteorology’s Jess Lingard explained that fog was cloud that formed on the ground.

“Fog forms when we have moist, cold air and clear skies overnight,” she said.

“We need those cloud free nights to allow that temperature to drop and, typically, we see these conditions after a cold front has gone through.”

The mercury fell to the dew point temperature, which is when water droplets start to condense out of the air, causing foggy conditions.

It’s the second morning this week that Perth has woken to hazy conditions and it can take until late in the morning to dissipate as the sunshine breaks through.

“As we’ve seen again today, like we saw on Tuesday, what happens is we’ve got this sort of higher cloud starts to move in during the morning and it stops and blocks out a bit of that sunshine from warming us up,” Ms Lingard said.

With cloudy conditions looking to be settling in for the next few days and some rain about, it’s unlikely we’ll see a foggy morning again until next week.