Water Life
Gundul

new mobs for your river and sea water

Placeable Buckets for Catching Rainwater
Noodlemire

Allows empty buckets to be placed as nodes in order to collect rainwater.

Climate API
TestificateMods

A powerful engine for weather presets and visual effects. Requires a weather pack like Regional Weather.

Sounds
AntumDeluge

A set of free sounds & API.