Lightening: Cranes are very susceptible to lightening strikes, so it is imperative that cranes operations cease whenever there is a threat of lightening.
When a lightening strike or thunder occur, all lifting operations must stop for 30 minutes. If there is a chance for inclement weather, you should monitor you weather very closely. There are multiple apps that will show bad weather and lightening strikes.
Wind: When items are being hoisted by crane, they can become very dynamic due to the wind. Items in the air can be caught by the wind creating a sail effect. This is very dangerous since it reduces control of the load by the operator.
It is recommended that crane operations cease when wind speeds reach 20 mph or greater but depending on the load being lifted 10-15 mph winds might be too great.