I prefer to use Climate Control/ Geographicraft to make world with huge biomes. When I set biome size = 7 or 8 on config ( 6 is large biome on vanilla ), sandstorm will appear on Desert biome, but no weather change on other biomes.

I think this is because Weather2 uses temperature gradients to spawn storms. With large biomes you dot have that gradient so you don't get many. I would try changing the Odds of Land Based Storm from -1 to 300 or so in the config.

A good idea, havent checked out large biomes yet but yeah it requires hot and cold biomes within the simulated area so large biomes probably makes that less likely

Thinking about it further, I'm probably not going to change the way my storms decide to become a deadly storm anytime soon, so just activate use of 'Odds of Land Based Storm' config as FunnelVortex said. The less idea alternative is setting the loaded chunk area to much larger, and increasing the weather simbox size in config.