(CNN)At least 189 people are dead and hundreds more remain missing after catastrophic flooding hit large swaths of western Europe, with tens of thousands unable to return to their homes and many still left without access to power and drinking water.

The flooding, caused by unprecedented rainfall, has hit parts of western Germany before shifting to neighboring Belgium and the Netherlands.

Several areas across the southern Netherlands remain evacuated after the river Maas rose to levels not seen in over a century on Saturday. In Venlo, a city that sits right on the Maas, 10,000 people had to leave their homes.

The rapidly rising water levels forced volunteers and the military to race against the clock on Saturday to prepare the city for the flooding. They produced sand bags and put up flood defenses while engineers focused on strengthening the dikes after one such embankment broke in the South Limburg province on Friday, causing large-scale flooding in the surrounding areas.

The preparation paid off -- the Venlo regional security agency said the dikes and flood defenses held overnight and no major flooding was expected.

Meanwhile in Germany, the true scale of the destruction brought by the floods was being revealed as the water subsided over the weekend, leaving behind devastation, mud and chaos.

Entire towns, train lines and roads were swept away and at least 158 people have died in what the German President Frank-Walter Steinmeier described as the "worst natural disaster" in a century.

By far the most deaths were reported in the western state of Rhine-Palatinate, where 110 people lost their lives, according to a statement issued by Koblenz police on Sunday.

Visiting Schuld, one of the worst hit towns, on Sunday, German Chancellor Angela Merkel said the devastation was "surreal."

"It is shocking -- I can almost say that the German language doesn't have words for the devastation," she told reporters in the town of Adenau, in Rhineland-Palatinate. Merkel promised her government would provide financial aid quickly.

Speaking alongside Merkel, Rhineland-Palatinate state premier Malu Dreyer said the area was "a place of horror and destruction."

Pope Francis expressed his solidarity with the regions hit by the disaster. "May the Lord welcome the deceased and comfort their loved ones, may he sustain the efforts of everyone who are helping those who have suffered serious damage," he said during an address in the Vatican on Sunday.

This aerial photo shows flooding in Erftstadt, Germany, on July 16.

Water flows over a square in front of a house in Bischofswiesen, Germany, Saturday, July 17.

A regional train sits in floodwaters at the local station in Kordel, Germany.

Water from the Ahr River flows past a damaged bridge in Schuld.

Houses are damaged by flooding in Insul, Germany, on Thursday.

In Belgium, the national Crisis Center said Sunday the situation was gradually improving throughout the country and that the areas hit by the floods are "out of imminent danger." It said search for victims continues and that the biggest concern at the moment was a lack of drinking water in some of the worst-affected areas. At least 31 people have died in the country, according to the center.

"Rescue operations have concluded, but search operations are still ongoing in a number of areas," the center said in a statement.

The devastating floods came after parts of western Europe experienced historic levels of rainfall, with more than a month's worth of rain falling in 24 hours.

Cologne, in North Rhine-Westphalia, recorded 154 millimeters (6 inches) of rainfall in the 24 hours to Thursday morning, which is nearly double its monthly average for July of 87 millimeters. In the Ahrweiler district, 207 millimeters (8.1 inches) of rain fell in only nine hours, according to the European Severe Weather Database.

The downpours resulted in extreme flash flooding, with water levels rising within minutes.

While it's too early for scientists to say how big a role climate change has played in causing this particular flooding, extreme rain events like the ones seen in western Europe this week are becoming more common and more severe.