Terrain Ground, lerp Grass and Snow in Cities: Skylines in C#

Hey guys, I am working on a Seasons Mod for Cities: Skylines. My way is kind of good, and I found a way to change the ground texture to a snowy one by using

mat.SetTexture("_TerrainGrassDiffuse", grassTexture);

So that is working fine, but i dont want a hard cut between the seasons. So I came up with this idea: Lerping between the snow and the grass texture. Googled much, but I didn't come up with anything which works. So I want a lerp which fades in the snow texture and fades out the grass texture by a given amount of time, so I think a lerp is right here. I have no access to the shader, cause its a mod, and I would need decompiling for that.. Any chance to do that? Thanks!