Full excerpt from "The God of Small Things" a novel by Arundhati Roy
May in Ayemenem is a hot, brooding month. The days are long and humid. The river shrinks and black crows gorge on bright mangoes in still, dustgreen trees. Red bananas ripen. Jackfruits burst. Dissolute bluebottles hum vacuously in the fruity air. Then they stun themselves against clear windowpanes and die, fatly baffled in the sun.
The nights are clear, but suffused with sloth and sullen expectation.
But by early June the southwest monsoon breaks and there are three months of wind and water with short spells of sharp, glittering sunshine that thrilled children snatch to play with. The countryside turns an immodest green. Boundaries blur as tapioca fences take root and bloom. Brick walls turn mossgreen. Pepper vines snake up electric poles. Wild creepers burst through laterite banks and spill across the flooded roads. Boats ply in the bazaars. And small fish appear in the puddles that fill the PWD potholes on the highways.
I agree the sentence is confusing as written. The trick is to recognize that what the children "snatch" are "spells of sharp, glittering sunshine". It's a figurative way to say that, in a season with mostly bad weather, children quickly take advantage of any good weather that comes along.