We're in a major area here for thunderstorms, and they can strike at any time although they are more common in summer. 4 years ago a lightning strike from what was pretty much a cloudless sky killed a guy sitting under a tree having his lunch, so it focused peoples minds wonderfully.
We have a system of detectors all round the perimeter of the site that can detect lightning discharges at a maximum of 50 miles distance. If a strike occurs at 30-50 miles we go on a low level (yellow) alert and work continues normally. If a strike occurs in the 10-30 mile range we go on a medium (orange) alert. Work continues but everyone working outside has to be aware of where their nearest lighning shelter is. If a strike occurs at less than 10 miles we go on high (red) alert and all outside work is stopped. On this highest level of alert all personnel must be either inside a building, in a vehicle with the windows rolled up, or in an approved lighning shelter. If we have a red alert then we must go at least 30 minutes with no strikes inside a 10-mile distance before the alert is lifted, even then it might only be lifted to orange level if we are still seeing strikes in the 10-30 mile range. However even during red alert the operation of all mining/earthmoving equipment continues as normal. That said we have no electrically-powered equipment like draglines or shovels, all our kit is diesel-powered.
In the past I've seen us go on red alert around lunchtime and not go out of it until well into the evening. It plays havoc with construction, not so much with mining.