Sioux Falls, South Dakota

... Severe Thunderstorm Watch safety rules...

A Severe Thunderstorm Watch means that conditions are favorable
for the development of severe weather in the designated area.
During a watch there is no cause for immediate concern. You should
go about your normal business... but be on the lookout and keep up
to date on the latest weather developments. Public safety
officials should activate prearranged plans.

A Severe Thunderstorm Warning... on the other hand... means that a
severe thunderstorm has been sighted or indicated by radar. People
in the path of the storm should take immediate action to safeguard
themselves and their family.

Technically speaking... a severe thunderstorm is defined as having
wind gusts which exceed 58 mph and/or hail at least 3/4 inch in
diameter. However... as these storms develop... they can be
accompanied by tornadoes. Listen to NOAA Weather Radio or other
local media to learn if a warning has been issued for your area.
Also... keep a close watch on the thunderstorms as tornadoes can
form quickly. If you see a tornado... move quickly into a basement.
If none is available... seek shelter in a small interior room on
the lowest floor and stay away from outside walls... doors and
windows. In schools... factories or other institutional type
buildings... stay out of auditoriums and gymnasiums.