A tornado is a violent, dangerous, rotating column of air which is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. Most people fairly consider tornado as an unstoppable destructive force. However, it is important to now the difference between different kinds of disaster for each of them represents different level of a threat.

60% of all tornadoes are FO (40 - 72 mph) and F1 (73 - 112 mph) categories. They will only last for about 10 minutes.

Stronger tornadoes of F2 (112 – 157 mph) and F3 (158 - 206 mph) categories are considered to be around 30% percent of all tornadoes and will sustain active around 20 minutes.

Tornadoes of F4 (207 - 260 mph) category can last longer than an hour. This group covers about 7%.

While only 3% of tornadoes are considered violent, including F5 (261 - 318 mph) and F6 (319 - 379 mph) category.

It’s important to know those basic terms for tornado warnings are only initiated then actual whirlwind has been seen or at least indicated by radar. Unlike a hurricane announcement dealing with tornadoes people only have a short time limit (sometimes only few minutes) to take an appropriate cover. So it’s important to get maximum information from even a short notice, instantly figuring out particular threat level.

If tornado watch mode is activated that means tornado forming is possible in the area. The most important thing to do is to stay tuned on a radio or television for further advisories, until you were told that it’s OK to let your guard down. Just as previously explained the reason is simple: unlike any other disasters tornado may appear in a few minutes after a warning has been given.