Storm Boris has wreaked havoc across Central and Eastern Europe, causing record rainfall and flash floods that have claimed at least five lives in Poland and Romania, forced hundreds of people to evacuate, and left many stranded as of Sunday.

A slow-moving low-pressure system that arrived on Friday and is expected to linger for days has unleashed a month's worth of rain in just 24 hours across Poland, Romania, Austria, the Czech Republic and Hungary, news agencies reported.

Rising floodwaters have overwhelmed emergency services in the Czech Republic, Poland and Austria, while Romania faced tragedy with four flood-related fatalities on Saturday, amid unprecedented downpours.

Rescue services in Romania battled severe flooding in eastern counties, particularly Galati and Vaslui, where the four deaths were reported.

Romania's President Klaus Iohannis addressed the flood crisis on social media.

"Severe floods that have affected a large part of the country have led to loss of lives and significant damage," he said.

"We are again dealing with the effects of climate change, which are increasingly present throughout the European continent, with dramatic consequences on people. We must continue to strengthen our capacity to anticipate extreme weather phenomena," he added.

In the Czech Republic, river waters swelled to alarming levels in many areas, with authorities evacuating hundreds, including hospital patients in the southeastern city of Brno.

More than 70 areas received the highest flood warnings, with officials from the Czech Hydrometeorological Institute stating such "extreme floods" occur only once a century in these regions.

In Austria, 24 villages in the northeast province of Lower Austria were declared "disaster zones" and evacuated. A firefighter battling flooding in Lower Austria was killed, Austrian Vice-Chancellor Werner Kogler said on social media.

"We are experiencing difficult and dramatic hours in Lower Austria," stated the governor of the province, Johanna Mikl-Leitner.

"For many people in Lower Austria, these will be the hardest hours of their lives," she added.

In Poland's second-largest city, Krakow, which lies on the Vistula River that has reached extreme low water levels in recent months due to record-breaking heat waves, severe flooding forced resident evacuations and disrupted public transportation.

In southwestern Poland's Klodzko district, one person drowned and 1,600 residents were evacuated.

After meeting with a crisis management team in Klodzko town on Sunday, Poland's Prime Minister Donald Tusk emphasized the gravity of the situation.

"The situation is very dramatic, it's most dramatic in Klodzko county," Tusk said.

In Slovakia and Hungary, heavy rain is making flooding worse along the Danube River, keeping rescue workers busy.

Slovakia declared a state of emergency in its capital, Bratislava, due to severe flooding. In Germany, rising water levels have affected southern and eastern regions, with authorities issuing flood warnings for rivers in Saxony.

The floods in Central and Eastern Europe follow an unusually hot early September in the region and Earth's hottest summer on record. Climate change is intensifying rainfall patterns, reported Euronews.