Over the past twelve years, we've seen tens of thousands of tornado warnings across the United States. Almost every major city east of the Rocky Mountains has seen a tornado warning at some point since 2002, and the resulting maps are pretty cool looking.
The National Weather Service began issuing "storm based warnings" in 2007, which limited the scope of tornado, severe thunderstorm, and flash flood warnings to the immediate areas that were impacted by the warning. Before 2007, warnings were issued on a county basis, even if only a small part of the county was affected by severe weather.
These maps show all 38,728 tornado warnings issued between January 1, 2002 and around midnight on July 23, 2014. Over that twelve-and-a-half year span of time, there were three states that saw every square inch of land go under a tornado warning at least once: Mississippi, Alabama, and Tennessee. Arkansas and Indiana came very close to complete coverage, but there was one extremely small area (about a few square miles each) that didn't go under a warning in each state.
Be sure to expand the maps using the link on the top-left of each image, as compression distorts the details.
Northeastern United States:
Southeastern United States:
Mississippi, Alabama, and Tennessee with 100% Coverage:
North-Central United States:
Central United States:
Southwestern United States:
Northwestern United States:
Although there have been two recorded tornadoes in Alaska since 1950, the National Weather Service has never issued a tornado warning in the state.
For the heck of it, here's a count of all the tornado warnings issued by each National Weather Service office since January 1, 2005, proving once again that Dixie Alley is alive and well:
[All marked warning maps by the author, total tornado warning count map by IEM]
[Correction: The NWS started issuing storm based warning polygons in 2007, not 2002 as I originally stated. I've fixed the error.]