Why do ants mound pop up after it rain ?
Because the water filled the ground, and they don't swim in good health.
Similar is true for earthworms. They tend to be at the surface after a rain. The water going through the soil made sand nose-dive from their ceilings so they clean it out of their home. Because the sand is waterlogged, it mounds up higher so you see it more.
not sure about the rainfall but red and mounds pop up so the red ants can push their baby sacks (young ants not but born) up nearer the top to retain the heat from the sunlight.
not an answer to your question i guess but its something i learn ages ago.
Answers: because they all put their brollies up.
My guess would be that their home got wet through with the rain and they're building up above the ground until the ground dries. i doubt anyone would be capable of answer this question, but my guess is thier old home get flooded