Several watch-and-act alerts are in place across Tasmania after widespread record-breaking rain across the state's top half spanning days.

Areas on alert include near the Meander River, North Esk River, South Esk River, and Macquarie River.

The North Esk and South Esk Rivers were still yet to peak on Saturday afternoon, and authorities would monitor them closely over the next 36 hours, Acting Premier Michael Ferguson said.

Floodwaters would continue to move downstream over the weekend in the Tamar river system, the Bureau of Meteorology said.

State Emergency Service acting director Leon Smith said rainfall in some areas outnumbered falls in mid-2016, when three people were killed.

"In the northwest, we've already seen the peak. All of the accumulated rainfall at altitude has now made its way through the landscape into the riverine systems (and it) is now dissipating," Mr Smith told reporters on Saturday morning.

"In the northern region, we haven't peaked.

"Due to the complexity of the catchments, we will see peaks and ebbs during the next 24 hours."

Mr Smith urged people in the northwest to remain vigilant and said residents had to be methodical in their return.

Reports that people had circumvented roadblocks were "extremely concerning", he said.

While roads may appear to be free of water, they had to be assessed for damage, Tasmania Police Assistant Commissioner Jonathan Higgins said.

"We can't have a police officer at every single road closure ... but there is a very visible police presence in the north and northwest of the state where there are roads closed," he said.

Police had to rescue some people who were taking risks with the floods, Tasmania Police northern district commander Stuart Wilkinson said.

The acting premier warned that while the wind and rain have eased, Tasmanians could not yet get back to normal life.

"We're not out of the woods yet at all - our waters are in fact still rising in a number of catchments and river systems," Mr Ferguson told reporters on Saturday afternoon.

"This is counterintuitive. With the rain effectively having abated, in fact the water is surging ... through the river systems, and there are two river systems that are still seeing waters predicted yet to peak.

"That means that there are yet more properties that can be subject to inundation (and) could be still subject to an evacuation order."

Authorities were monitoring the North Esk and South Esk Rivers "like a hawk", Mr Ferguson said.

Up to 500 homes were within flood zones, but authorities expected the number inundated to be far fewer, he said.

It remains unclear when the port of Devonport will reopen after it was closed to commercial operations on midday Thursday ahead of flooding in the Mersey River.

The closure forced the Spirit of Tasmania ferry operator to cancel four Bass Strait sailings.

Australian Associated Press