You can cast this spell only at the beginning of your turn, before you take any other actions.

After casting blade storm, you can take a full-round action to make one attack with each melee weapon you are currently wielding against every foe within reach.

If you wield two weapons, or a double weapon, you can attack each foe once with each weapon or end, using the normal rules for two-weapon fighting.

So, a ranger wielding a longsword and a short sword could attack each opponent he can reach with both weapons.

You can attack a maximum number of individual targets equal to your character level.

If you choose not to spend a full-round action in this fashion after casting the spell, the spell has no effect.