I used Hail and then Blizzard in gen 3 specifically Emerald and it has not missed am I lucky or something? This was with Walrein with thick fat but that does not help with accuracy I also used it twice neither missed which is surprising
Each time you use blizzard (assuming no changes to anyone's accuracy or evasion stats), the chance to hit is 70%. source So if you use it twice, the chance that it hits both times is 70% * 70% = 49%.
Blizzard ignores accuracy under hail like how thunder ignores accuracy under rain.