Two game rules, snowrealmagic:blizzardStrength (1–8, max layers) and snowrealmagic:blizzardFrequency (N/10000 per tick per chunk), make snow blocks fall from the sky. Have fun!

Datapacks can change which blocks interact with snow by adding to the mod's block tags. To append entries, create the file under the snowrealmagic namespace in your datapack, e.g. data/snowrealmagic/tags/block/containables.json:

(Also see Editing tags using KubeJS)

{
    "values": [
        "mymod:my_flower",
        {
            "id": "#mymod:my_pebbles",
            "required": false
        }
    ]
}

Available tags:

• containables: Blocks that snow can be placed into, turning them snow-covered. (Default: plants, offset_y, expand_model and #c:chains)
• not_containables: Blacklist. Blocks here can never contain snow, even if they are in containables. (Default: #minecraft:leaves)
• plants: Plants that become snowy plants when snow covers them. Compared to #containables, it will be able to be detected by shaderpacks to make them swing, but as far as I know, no shaderpacks support this yet. (Default: dead bush, flowers, saplings, mushrooms, etc.)
• entity_inside: Snow-covered blocks that keep their touch effects, e.g. wither rose damage. (Default: wither rose, sweet berry bush)
• animate_tick: Snow-covered blocks that keep their ambient particles, e.g. firefly bush. (Default: wither rose, open eyeblossom, dry grass, firefly bush)
• offset_y: Flat blocks that are rendered slightly raised when snow-covered, to avoid z-fighting with the snow layer. (Default: pebbles, twigs and similar decorations from supported mods)
• expand_model: Blocks whose model should be treated as a full cube when snow-covered. Used for compat with mods like vertical slabs.
• cannot_accumulate_on: Snow will not naturally accumulate on top of these blocks. (Default: hay block, slabs)

Resource packs can change how a block looks when it is snow-covered. Add a .json.mcmeta file next to the block's model file with an srm section pointing to the model to use instead. For example, assets/minecraft/models/block/dandelion.json.mcmeta:

{
    "srm": {
        "model": "mypack:block/snowy_dandelion"
    }
}

The snowy model is a regular block model. For cross-shaped foliage you can parent the built-in template, which renders the plant together with a snow overlay:

{
    "parent": "snowrealmagic:block/snowy_cross",
    "textures": {
        "cross": "block/dandelion",
        "snow": "mypack:block/snowy_dandelion"
    }
}

For double-height plants such as tall grass, put the mcmeta on the top-half model and add an overrideBlocks list with the block ID, so the upper half also renders snowy:

{
    "srm": {
        "model": "mypack:block/snowy_tall_grass_top",
        "overrideBlocks": ["minecraft:tall_grass"]
    }
}

This feature requires the client config snowVariants to be enabled (it is by default).

• snowGravity (default: true): Snow layer falls like sand. [Performance impact: low]
• snowMakingIce (default: true): Falling snow becomes ice when it touches water. [Performance impact: none]
• snowAlwaysReplaceable (default: true): Snow layer can always be replaced by other blocks, as long as it is not full. [Performance impact: none]
• thinnerBoundingBox (default: true): Shrink the collision box of the snow layer. [Performance impact: none]
• snowNeverMelt (default: false): Snow layer never melts. [Performance impact: none]
• snowSpawnMaxLightLevel (default: 9): Maximum light level for snow to spawn. [Performance impact: none]
• snowPersistMaxLightLevel (default: 11): Maximum light level for snow to not melt. [Performance impact: none]
• snowReduceFallDamage (default: true): Reduce fall damage when landing on snow, depending on the snow layers. [Performance impact: none]
• sustainGrassIfLayerMoreThanOne (default: true): Prevents grass block from turning into dirt when snow layer is more than 1. [Performance impact: none]
• sneakSnowball (default: true): Sneak+use on snow layer to obtain snowball, consuming one layer of snow. [Performance impact: none]
• fancySnowOnUpperSlab (default: true): Snow layer on upper slab will render snow overlay on the side of the slab. [Performance impact: low]
• rightClickToggleFancySnow (default: true): Right click with empty hands to toggle the fancy snow overlay on any snow layer. [Performance impact: none]
• mobSpawningMaxLayers (default: 8, range: 1–8): Maximum layers of snow for mobs to spawn. [Performance impact: none]
• snow-cover.placeSnowOnBlock (default: true): Snow can be placed on some blocks to make them snow-covered. [Performance impact: low]
• snow-cover.placeNaturally (default: true): Snow can be placed on some blocks not only by player, but also from snowfall or world generation. [Performance impact: low]
• snow-cover.replaceWorldgenFeature (default: true): Replace the vanilla world generation feature to also generate snow-covered blocks. [Performance impact: low]
• snow-cover.restoreOriginalBlocks (default: false): If you want to uninstall this mod, you can restore snow-covered blocks to their original blocks on chunk loaded. [Performance impact: low]
• accumulation.accumulatesDuringSnowfall (default: false): Snow layer accumulates during snowfall. [Performance impact: medium]
• accumulation.accumulatesDuringSnowstorm (default: true): Snow layer accumulates during thundering. [Performance impact: medium]
• accumulation.maxLayers (default: 6, range: 0–9): Maximum layers of snow that can accumulate. 9 is unlimited. [Performance impact: low]
• accumulation.snowAndIceMeltInWarmBiomes (default: false): Snow and ice will melt in warm biomes. [Performance impact: low]
• accumulation.naturalMelting (default: true): Snow melts with time if its layer is more than 1. [Performance impact: medium]
• accumulation.smoothAccumulation (default: true): Snow layer will accumulate and melt more smoothly. [Performance impact: low]
• integration.accumulationWinterOnly (default: false): If you have a mod that adds seasons, snow accumulation only happens in winter. [Performance impact: none]

• particleThroughLeaves (default: true): Generates snowflake particles under snow that is above leaves. [Performance impact: low]
• snowVariants (default: true): Some snow-covered foliage will be rendered differently. [Performance impact: low]