Nor do mine... In Singles anyways, where it counts.
Hydro Pump doesn't have a secondary effect, hits only a single target, and can't have perfect accuracy via weather. Blizzard > Hydro Pump.
It's also noteworthy that Blizzard has way shittier accuracy outside of Hail, and that Rain as a weather condition is all around better. Does Blizzard get a power boost in Hail? I think not!