Temporary Flight Restriction (TFR)
If you are flying your unmanned aircraft, you know that you are subject to the same restrictions as jetliners when it comes to the FAA.
Here's a site that tells you if there are any Temporary Flight Restrictions (TFR) in your area before you send your UA out crop scouting or before your son fllies his quadcopter out to look at flowers.
The TFR is announced by a NOTAM (Notice to Airmen). The most likley reasons for a TFR are VIP visit (some government big-shot is flying in), HAZARD (forest fire, volcano eruption), SECURITY (missile launch, government restricted areas) SPECIAL (I dont' know on this one). There are also TFR over major sports events such as Division one college football games, big races, Super Bowl, World Series and othe places where large crowds gather.
TFR can be of all sizes and shapes and can extend to various altitudes. Many VIP TFR are 30 nautical miles in diameter, but check first and don't count on that.
Sports TFR are usually from one hour before to one hour after the event. Other TFR are announced in the NOTAM.
Don't count on any other source than the government site for the definitive TFR. The can change momentarily and if you got old lnfo from an unofficial source it won't save you if the feds send an F-16 after you.