Bureau of Meteorology explains why the weather has felt warmer in WA

The Bureau of Meteorology (BoM) has confirmed that humidity levels were above the March average for many areas across WA recently.

It's classified as humid when the dew point temperature is forecast over 15 or 16 degrees Celsius - which occurred last weekend and early this week.

In Geraldton the average monthly dew point temperature is 15.6oC.

From March 11, it started to exceed that, hitting 18.7oC on Friday.

For those further south, York's average dew point for March is a low 12oC, however from March 12 it hit 15.5oC and was 17.5oC on Sunday.

Fog has also increased, including in areas along the Great Northam Highway into Northam.

BoM duty forecaster Jessica Lingard said this week has been more humid due to some unusual trough activity.

"Usually our troughs sit vertically, so to speak, if you're looking at a map," Ms Lingard said.

"They lie down the west coast, but the tail of this trough has been sitting over the south west of the State while the head of the trough, the northern end of it, has been moving eastward like it normally would."

Ms Lingard said this meant air circulated at the base of the trough where dry air came off the land and collected moisture from the ocean, before returning to the land.

This situation is commonly seen along the Pilbara coastline, resulting in fog and humidity.

With the higher moisture content in the air, it's no wonder that there was also rain last weekend.

BoM recorded 22.6 millimetres at Nyabing, while Jacup had 21.2mm, Mount Barnett 21mm and Ongerup had 19.6mm.

With continuing afternoon monsoonal thunderstorms in the Kimberley, some locations received more than 10mm.

The falls in the southern half of WA are due to an upper trough moving through, which Ms Lingard said favoured thunderstorm development.

"The upper trough started further to the west of the State around Friday and just as that trough has moved eastwards it has taken the thunderstorms with them," she said.

"The thunderstorms that passed through then on Monday, Tuesday in the Eucla district and the Southern South Interior - they are still that same system that went through the South West."

Moving into the weekend a cold front is expected late on Friday, early Saturday.

"The cold front could bring some rainfall into the South Western parts of the agriculture areas, then the coast and the South Coast will see a good drop as well," Ms Lingard said.

"This time of year, autumn, we get a few hot days with the troughs down the west coast then we get a few days of weak cold fronts.

"We flip flop between the summer patterns and winter patterns, hopefully we will see a few more of the wintery patterns and get some rainfall where it's needed."

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