England's clash with Mexico in the World Cup is potentially at risk of being pushed back due to storms over Mexico City.
Lightning storms are relatively rare in the UK, where conditions are too cool, too cloudy and the seas around these isles cool the air down considerably. That prevents storms from former as frequently as they do across larger continents. Even when we do get them, they tend to be pretty tame.
So if you're wondering 'well, it's just a storm, what's the big deal' - think again. They can be no joke.
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FIFA lightning storm delay rules
Per FIFA protocols, if there is lightning within a eight-mile radius of the stadium at the time doors are due to open, fans and players alike will not be permitted to enter the stadium.
If a storm begins when the everybody is already in the ground, or even while the game is in progress, then play will be stopped and will not be able to proceed until there has been 30 minutes without a lightning strike within eight miles of the stadium. Every new strike resets the 30 minute timer.
Eight miles may sound excessive, but keep in mind that lightning can strike more than ten miles away from a storm.
There are also risks of people being injured by ground currents, where energy travels through the ground following a strike; contact injury, where electricity is discharged from a conductive material being touched; or side flash, where a charge can travel from a struck object to people nearby.
The odds of any one specific person being struck by lightning are obviously low, but with over 80,000 people expected at Estadio Azteca, the odds of someone being struck, either inside the ground or while travelling to the stadium, are multiplied accordingly.
The risk assessment essentially boils down to this: the chance of something happening are low, but if something did happen, it could be catastrophic. Lightning strikes can cause death, serious injury and mass panic.
Getting the football played on time simply is not worth taking that chance. For games played in the US, it's not just a FIFA thing: a very similar protocol is in affect across the United States under guidance from the National Weather Service.
Two games have already been delayed by storms at this World Cup.
The second half of France's meeting with Iraq in the group stage was supended for around two hours after lightning was reported nearby during the interval.
Mexico's meeting with Ecuador in the last round meanwhile had kick-off delayed by an hour after storms near to Estadio Azteca.
