You forgot your umbrella - again. (Or the damn weatherman got it wrong - again.) Either way, your leather bag got soaked, and you need to know what to do. Well, here’s your first tip: act fast.
Here’s the rest:
Gently wipe off any standing water and allow it to naturally dry to the point of being damp - but not dry. (Do NOT apply unnatural heat, like a blow dryer.) For a jacket, hang it on a wide, padded hanger. For bags or shoes, stuff them with crumpled newspaper to help hold their shape.
While the leather is still slightly wet (just damp), apply a reasonably thick coat of leather conditioner. Massage the conditioner into the surface of the leather and leave it to dry for several hours or overnight. The conditioner will penetrate the leather and replenish the natural oils that were stripped when it got wet.
If it seems overly dry in places, apply additional conditioner to those areas and buff the entire surface of the leather. (After you’ve addressed the current wet leather situation, you can apply a water and stain repellent before it gets wet again.)