Motorists are reporting flooding and slips on State Highway 29.

A SunLive reader has emailed in to say there are slips and flooding across the highway by McLaren Falls Road.

"Police are in attendance.

"Expect significant delays as traffic is building."

Significant delays are being reported on SH29. Image: Google Maps.

Earlier this morning, the MetService warned there is a risk of thunderstorms and downpours across the North Island today.

A low pressure system is meandering in the Tasman Sea for most of this week, which is pushing humid air onto the North Island.

High humidity combined with heating during the afternoons work together to create a favourable environment for thunderstorm development, and today is the day when this risk is greatest.

The area with the highest risk of experiencing thunderstorms and localised downpours today is over the North Island from Tauranga southwards, excluding the western coastline south of Cape Egmont.

"Downpours from thunderstorms are bursts of heavy rain falling at a rate of more than 25mm per hour. Such high amounts of rain falling during a short period can cause surface or flash flooding in any places where this may happen," says MetService meteorologist Dan Corrigan.

"These conditions, along with poor visibility, make driving hazardous as well.

"The tricky part is that it's nearly impossible in this kind of weather situation to pinpoint exactly where each thunderstorm cloud will develop and move. Not everywhere will be affected by a thunderstorm, and any resultant downpours will be localised."