According to the Lviv Regional Center for Hydrometeorology of Ukraine :
in the Lviv region at night and in the morning on April 18 in some places, on April 19-20 throughout the territory, severe frosts of 0-5°.
in Lviv city on April 19-20, at night and in the morning, severe frosts of 1-3°.
(Hazard level II, orange)