STOCKHOLM, May 30 (Xinhua) -- At least 13 Swedish municipalities have introduced a hosepipe ban and another 30 have urged residents to use water sparingly as a heat wave continues to grip the Nordic nation.

The warnings have been issued in towns across Sweden, from the northern town of Boden to Vellinge in the south, as an unusually warm May has brought soaring temperatures to the country and many water plants have reached maximum capacity, Swedish Television reported on Wednesday.

While a heat wave during the summer holiday season does not usually put this much strain on the country's water plants, this year the warm weather hit the country unusually early.

In the month of May, the industries are still active and people have not yet left the country for their summer holidays, Fredrik Vinthagen, head of communications at the Swedish Water and Wastewater Association (SWWA) said.

He added: "Everyone is still at home while, at the same time, there is great need to water newly planted gardens and to fill up swimming pools."

Groundwater levels also reached a critical low last summer when hosepipe bans were introduced in some Swedish municipalities. However, there are more such bans this year and they have also been introduced earlier than usual. The last time groundwater levels were as low as in 2017 was in the mid-1970s.

However, according to the Geological Survey of Sweden, the heavy rain and snowfall during the past fall and winter has meant that groundwater levels are currently satisfactory, groundwater geologist Emil Vikberg told Swedish Television.

"The situation is satisfactory right now in large parts of the country. However, in some parts of southern Sweden we are beginning to see groundwater levels that are below normal and we are also seeing sinking levels in those areas," Vikberg said.