(CNN) -  A series of deadly storms that pummeled Arkansas,
Missouri and other states this week reminds us that tornado
season is upon us once again.  Tornadoes kill 70 people and
injure 1,500 more every year in the United States, according to
the National Oceanic and Atmospheric Administration. The average
speed of a tornado is 30 miles per hour and they can move more
than 50 miles on the ground, leaving huge amounts of destruction
in their wake.  Getting the latest warnings when tornadoes are
headed your way and knowing what to do before, during and after
one hits are all key to staying safe. A handful of apps can help
you stay on top of impending dangerous weather. Keep in mind
that you'll want to save power on your smartphone in case the
electricity goes out, so use it sparingly.  Here are some
digital tools to help you through a storm safely.  NOAA Weather
Radio  Getting advanced warning of impeding tornadoes is key. If
the electricity goes out and you can't watch weather updates on
TV, you can switch to