ZAGREB, Croatia (AP) — The first snow of the season snarled traffic in parts of the Balkans on Wednesday as authorities warned motorists of slippery roads and doctors in Slovenia urged extra caution against accidents with medical facilities already overwhelmed from treating COVID-19 patients.

Croatian authorities barred trucks with trailers from all roads leading toward the Adriatic Sea coast as long columns of vehicles formed in some areas.

Strong wind caused problems on roads closer to the coastline, and double-decker buses, motorcycles and cargo vehicles were not allowed through. Big waves led to disruptions in ferry service to Croatia’s islands.

Slovenia reported occasional traffic interruptions caused by sliding vehicles on sections of main motorways. The Vrisc mountain pass in the Alpine nation’s northwest was closed to vehicles except cars with snow chains.

In Slovenia’s capital, Ljubljana, doctors at the main clinic urged citizens to be careful since the hospital was overburdened due to the coronavirus, the official STA news agency reported. The Adriatic Sea coast town of Piran issued flood warnings for lower areas.

Snow also fell in western Bosnia, where sleet warnings were issued as well. Authorities recommended “minimum driving in this area tonight and tomorrow.”

The wintry weather in Bosnia added to the hardships of thousands of migrants hoping to reach neighboring Croatia, a European Union member. Many have been stuck in Bosnia near the border and sleeping rough in make-shift tents with no facilities.

Warmer weather is expected later this week in the region.