The US is enduring another bout of severe winter weather, as a succession of powerful weather systems brings heavy snow, freezing rain and extreme cold temperatures to much of the country.

Twenty-six states, from Texas to Massachusetts, were under storm warnings issued by the National Weather Service over the weekend, with many alerts remaining in place this week.

Heavy snow began falling in parts of north Texas and Oklahoma on Friday evening before pushing eastwards. By Sunday, swathes of the central and eastern US were experiencing either heavy snow or freezing rain, causing widespread travel disruption.

In parts of Mississippi, Tennessee and Kentucky, about 2.5cm (1in) of ice coated cars, roads, trees and downed power lines. Snow and freezing rain continued to track north-east into cities including New York and Philadelphia, where some areas recorded 30-50cm of snowfall.

Power outages are expected to last several days in some regions, with more than 800,00 households without electricity as of Sunday night. At least seven deaths have been linked to the extreme conditions. Widespread intense cold is now spreading southwards, with lows of -20C in parts of Texas.

Forecasters have also warned of an unusual hazard associated with the deep freeze: “exploding” trees. Rapid freezing causes water and tree sap to expand inside tree trunks, sometimes producing loud cracking or explosive sounds as wood and bark split under pressure.

Meanwhile, in Europe, the Portuguese meteorological agency has named another Atlantic low-pressure system, Storm Joseph, which is expected to bring further severe rainfall to the Iberian peninsula.

After Storm Ingrid brought strong winds, heavy rain and even snowfall to parts of the region in recent days, much of Portugal and north-west Spain is braced for exceptionally high rainfall this week. Up to 20cm could fall by Friday, with higher ground potentially receiving more than 30cm. The torrential downpours are likely to cause further disruption, with flooding a substantial risk.