In Australia, we have cricket ball sized hail in severe thunder storms LOL
Seriously, probably knowing a bit more about the physics involved in meteorology than in aircraft design and behaviour, you should never treat a storm with contempt. This is particularly true at certain times of the year (depending on region).
There has been enough research into storms now to know how they will affect an aircraft, whether on takeoff, in flight, or landing. I would imagine there is a threshold point that a storm must reach before airlines and ATC would start moving things around it (I also imagine this is well before the local Bureau of Meteorology would classify the storm as "severe").
Just out of interest, in Australia a thunderstorm is rated severe when one of the following events occur. 1) intense radar echoes are observed above a height of 8km; 2) hail stone exceeds 2cm in diameter; 3) wind gusts exceed 90km/h; 4) flash flooding is reported; 5) tornadoes are spotted.
Chances are that once a storm tower has headed through 8km in height, you are going to get some of the other stuff anyway. This is also the point where you close the airport if it is in the storm path.
On 14 April, 1999, a storm like this went right over the top of Sydney Airport. Hail was measured at 9cm in diameter, causing many thousands of dollars damage to aircraft. Some of the parked aircraft had to have wing panels and control surfaces replaced (up to B767 size aircraft).