Weather It is a weather-effect add-on for Blender from Blender Bits. It covers a range of conditions, from intense storms and heavy rain through to soft mists and snowfall, all of them customizable. A speed setting for the effects can be adjusted in the geo-nodes tab.
For added detail, it includes realistic rain bounce on surfaces and snow buildup on the ground. It renders in both Cycles and Eevee and is compatible with Blender versions 4.0 through 5.0 as an add-on, with Blender Extension compatibility noted. Documentation is included, and it's released under the GPL license.
One current limitation to be aware of: changing the size of the spawner also changes the speed of snow and rainfall. This can be fixed by adjusting the speed value in the geo-nodes tab. A demo video is available on the developer's page for a closer look.