The Spanish capital of Madrid was still trying to get back on its feet Monday after a 50-year record snowfall that paralyzed large parts of central Spain and was hampering the delivery of coronavirus vaccines.

The blizzard dumped more than 20 inches of snow in some areas, and a cold front was turning that fluffy snow into sheets of ice and crusted drifts. At least 700 roads were still not clear enough to drive without chains.

Temperatures were expected to drop to minus 12 degrees Fahrenheit in a large swathe of the country later Monday, according to the national weather agency, prompting authorities to urge people to exercise caution.

“We have some very complicated days ahead until the cold snap subsides,” Interior Minister Fernando Grande-Marlaska said at a televised news conference. “It is necessary to postpone any movement that is avoidable, for safety and in order to not interrupt the works in the road network.”

A new batch of 350,000 doses of the Pfizer-BioNTech coronavirus vaccine that Spain was expecting arrived at half a dozen airports Monday, but the doses destined for Madrid had to be diverted to the northern city of Vitoria.

The central government’s representative in Madrid, José Manuel Franco, told Onda Cero radio that the pharmaceutical company was working hard to ensure the arrival of the capital’s doses. Authorities said earlier that police escorts would help the vaccines get through the snow-clogged streets and highways.

In Madrid, civil protection and military battalions, aided by snowplows and bulldozers, managed to clear lanes for ambulances and emergency vehicles. Still, much of the city’s main services remained closed Monday, although some supermarkets and newsstands opened for the first time in three days.

Residents, some with spiked snow shoes and hiking sticks, warily tried to make their way on icy snow before disappearing into subway stations.

The underground train system has become the only viable way to commute to work, leading to scenes of overcrowding in train cars where keeping social distance was impossible. Commuter trains in Madrid and the high-speed railway between Barcelona and Madrid will resume later Monday, the national railway company said.

The airport, which had been closed since Friday evening, saw a dozen flights take off or land Monday and was expecting to ramp up to full operations.

Schools were closed Monday in the regions of Castilla La Mancha, Madrid and many other areas.