How can an airplane land if a hail storm damages the windshield?
In the EMB-145 the abnormal procedure for obscured windscreens is to secure items in the cockpit, open the side window and look through its opening.

There are more aircraft that share this procedure. 

Here is the QRH procedure for "Impaired or cracked windshield" in the EMB-145:

Associated Windshield Heating .............................. OFF

IF  only the outer layer (glass) is cracked, no action is 
    required

IF  inner layer of glass is cracked, proceed as follows:
    Cockpit Door ......................................... CLOSE
    Maximum Altitude ....................... 10,000 FT., OR MEA,
                                             WHICHEVER IS HIGHER
    Pressurization Manual Controller ........ 1 O'CLOCK POSITION

                    Wait 15 Seconds

    Pressurization Mode Selector ........................... MAN
    Cabin Delta-P ........................... SET EQUAL TO 1 PSI

    Note:  Pressurization Manual Controller must be used to set
           and maintain Cabin Delta-P at 1 psi while descending

    Airspeed .................................... BELOW 250 KIAS
    Smoke Goggles .......................................... DON
    In case both windshields are impaired:
    Cabin (below 10,000 ft) ....................... DEPRESSURIZE
    Airspeed ................................. MAXIMUM 140 KIAS,
                                                    MINIMUM Vref

IF  forward view through both wind screens is impossible, secure
    loose objects in cockpit and proceed:

    Note:  Intercommunication will be impossible with window 
           removed.

    Direct Vision Window ................................ REMOVE
    Landing must be made looking through the direct vision 
    window

                              * * * *