The "freedom convoy" is now into its fourth day, mostly protesting against Covid-19 vaccination regulations, with hundreds gathered on Parliament's lawn despite a trespass notice being issued.
Yesterday, more than 120 people were arrested in ugly scenes as protesters clashed with police.
Speaker Trevor Mallard confirmed he had ordered the sprinklers to be turned on as part of efforts to clear the protesters. He said the sprinklers will stay on through the night.
Mallard told 1 News: "They're not legally on the ground, so there is no problem adding a little to their discomfort."
Those camped out on the grounds of Parliament can expect some rough nights ahead if they intend to stay there because MetService has issued a heavy rain warning for Wellington over the weekend.
The weather warning is in place from 8pm tonight until 3pm on Sunday.
MetService has forecast periods of heavy rain, with up to 200mm expected to accumulate. Peak rates could be anywhere between 15mm to 25mm per hour.
The warning applies to Wellington and Wairarapa, excluding the Tararua District.
MetService meteorologist Lewis Ferris said the rain wasn't looking "overly heavy" until tomorrow afternoon.