Only usable before range is determined on the first round.
Both combatants and each of their retainers take 1 damage before range is determined each round. This damage cannot be prevented. A vampire can play only 1 Weather Control each combat.
As above, but the amount of damage inflicted increases by 1 each round.
Clarifications and Rulings
Multiple Weather Controls are cumulative. [TOM 19950710]
Weather Control's damage will occur even if combat is subsequently ended before range (by Mariel or Elysium: Arboretum, e.g.) [LSJ 19971110]