A blizzard is a severe snow storm characterised by poor visibility, usually occurring at high-latitude and in mountainous regions (WMO, 1992).

A drought is a period of abnormally dry weather characterised by a prolonged deficiency of precipitation below a certain threshold over a large area and a period longer than a month (WMO, 2020).

Hail is precipitation in the form of particles of ice (hailstones). These can be either transparent, or partly or completely opaque. They are usually spheroidal, conical or irregular in form, and generally 5−50 mm in diameter. The particles may fall from a cloud either separately or agglomerated in irregular lumps (WMO, 2017).

An ice storm involves the intense formation of ice on objects by the freezing, on impact, of rain or drizzle (WMO, 1992).

Snow is the precipitation of ice crystals, isolated or agglomerated, falling from a cloud (WMO, 2017).

A snow storm is a meteorological disturbance giving rise to a heavy fall of snow, often accompanied by strong winds (WMO, 1992).

Acid rain is rain which in the course of its history has combined with chemical elements or pollutants in the atmosphere and reaches the Earth’s surface as a weak acid solution (WMO/UNESCO, 2012).