State police spokeswoman Lt. Julie Lewis says if lightning is spotted within five miles of the site, operations will be suspended.
Light rain fell at midday Monday in the vicinity of the site near the town of Doyline (doy LEEN'). No lightning was expected Monday, but thunderstorms were forecast for Tuesday.
Officials estimate that more than half of Doyline's 800 residents heeded state police advice to evacuate in advance of the cleanup that began over the weekend.
State police say roughly 6 million pounds of an explosive artillery propellant was found improperly stored at the Explo Systems Inc. site.