When is a tarp really needed? There are a number of situations that could really use one. They can protect your possessions--or even you--from heavy rainfall and hailstorms to bright sunshine and strong winds.
A tarpaulin can be used to cover the ground itself. Whether this is to protect something on the ground or to keep dirt off of something that will be above the tarp, you should always consider whether someone will be walking on the tarp. If so, you'll want to use canvas tarps for this particular purpose instead of poly tarps. After all, a high quality plastic tarp can be dangerously slick to walk on!
A tarp should be included in every emergency kit. With a few other supplies, like rubber tarp straps, you can have shelter from the elements in a matter of minutes. If you're caught out in a storm, shelter should be one of your first priorities.
Covering a Leaky Roof
Long-term, the best way to deal with a roof leak is to have the roof repaired. But even in the best case scenario, such a repair does not happen immediately. But a tarp cover can help you immediately cover the roof and protect your home and your belongings from water damage until the roof can be repaired.
Covering a Pickup Load
A truck tarp can do double duty when covering a load: it can protect whatever is in your pickup bed, and it can keep whatever is in your pickup bed from flying out and into the road. Using a mesh tarp or a canvas tarp as your truck tarp allows it to remain breathable.