Seven people have died as extreme weather across Europe causes record flooding, hundreds of landslides, another heatwave and more wildfires.

Six deaths were reported as rescue workers battled heavy storms, floods, and landslides across Slovenia, Austria and Croatia while a woman died after she was hit by a falling tree in Lithuania

The devastating floods in Slovenia affected two-thirds of the country’s 2.1 million residents and brought international help to the scene, authorities said.

The flooding marked the worst natural disaster Slovenia has seen since gaining independence in 1991. Prime Minister Robert Golob, estimated the total damage at more than $US548.3 million ($A834.0 million).

“In these difficult times, Slovenia is not alone,” Golob’s office wrote. “We have many friends and international support, including from the EU, NATO and the US.”

In Croatia, authorities recorded high water levels as roads, fields and settlements were flooded, Croatian television HRT reported.

A state of emergency was declared in various parts of the country. Major damage to residential buildings was prevented as sandbags were used as makeshift dams.

In all three countries, however, the situation was expected to ease as water levels were dropping on Monday, according to authorities.

In the Czech Republic the heavy rainfall was easing up. In neighbouring Slovakia however, the rain continued on Monday and several rivers such as the Poprad River threatened to burst their banks.

In the Slovak Paradise National Park, gorges were closed to visitors. Several hiking trails in the High Tatras were also temporarily closed due to flooding.

Thousands of homes in Poland were experiencing power cuts following severe storms and heavy rain over the weekend, authorities reported.

In the very north-eastern region of Podlaskie, 7500 homes had no electricity on Monday, according to the utility PGE. In nearby Warmia-Masuria, the figure stood at 5000.

The German weather service DWD has forecast a severe storm for Monday and Tuesday in the Baltic Sea.

Ferry services to the northern German holiday islands of Hiddensee and Rügen have been suspended.

Gusts from the north-west could reach between 90km/h and 100km/h, in some cases they could reach hurricane strength of around 105km/h, the DWD said.

“This is extremely unusual at this time of year. We expect a storm like this in the autumn and not in the high summer,” said Michael Knobelsdorf of the DWD.

Storm Hans was brought heavy rainfall and violent thunderstorms to Sweden and Norway, leading to flooding, fires, water damage and disruptions to rail and ferry services.

Two carriages of a passenger train derailed near Hudiksvall, about 300 kilometres north of Stockholm, when the railway embankment gave way due to heavy rain, Swedish police said. Three people were taken to hospital – the extent of their injuries is unclear.

Norwegian meteorologists expected the situation in their country to worsen, predicting that Hans could become one of the most powerful storms in the past 25 years.

In the Baltic states, a severe thunderstorm led to heavy wind as well as hailstorms and rain in the Baltic States.

Buildings and vehicles were damaged and trees uprooted in Estonia, Latvia and Lithuania .

A woman died after she was hit by a falling tree in northern Lithuania, Lithuanian radio reported, citing emergency services.

In Estonia and Latvia, thousands of households were temporarily without power, according to media reports.

Meanwhile, Spain is being hit by the fourth heatwave of the summer and it is expected to continue at least until Thursday with an increased risk of forest fires, the weather service AEMET said.

The peak is forecast on Wednesday with temperatures of up to 44C in the region surrounding Madrid and in Jaen in Andalusia.

There were also several fires in Portugal. The most devastating destroyed some 7000 hectares, equivalent to the area of just over 10,000 football pitches, in the districts of Castelo Branco and Proenca-a-Nova in the centre of the country over the weekend.

The fire was brought under control on Monday, but about 1000 emergency personnel were fighting new fires in Odemira in the south-west, in Ourem in the centre and in Mangualde in the north of Portugal.

– AAP