How did a metre of ice cover the ground in Mexico?

Ben Domensino, 2 July 2019

Parts of Guadalajara, Mexico's third largest city, were covered by around a metre of hail on Sunday morning.

Locals woke to find a thick accumulation of hail in the streets of Guadalajara after an intense thunderstorm struck the city early on Sunday morning.

The ice was so thick in some areas that it buried cars, while the storms also caused damage to homes and businesses. Mexico's national agency for civil protection, the CNPC, reported that some communication infrastructure was also damaged and that health services treated three people for possible cases of hypothermia.

Ice covered streets in central areas of Mexico are not a common sight. Guadalajara, which sits at roughly the same latitude as Townsville, usually experiences daytime temperatures in the low thirties and overnight minimums in the high-teens during June. While this is too warm for snow, it's an ideal climate for thunderstorms.

Sunday morning's hail was produced by a towering thunderstorm cloud, in which temperatures were cold enough to produce large amounts of small hail.

When this hail reached the relatively warm ground in Guadalajara, it formed a slushy mix of hail and water. It's likely that this water-hail mix flowed into low-lying areas of the city, where it was able to gather into deep pools. The water would have either flowed into drains or evaporated, leaving behind the thick cover of hail on Sunday morning.

It's too early to know whether or not this extreme weather event was influenced by climate change. This information is usually deduced through an event attribution study some time in the future.