Web alarm clock for 2:44 p.m.
You are getting a cover ready for the gathered coconuts before the clouds open, rather than waiting for the first drops to fall. Set the alarm for 2:44 pm so you have a clear signal to spread the tarpaulin, secure its corners, and check that runoff will not reach the pile. That leaves enough time to finish the covering before 3:00 pm without rushing across a wet yard.
Your coconut-covering cue needs a device that will remain awake until the alarm sounds. A phone or laptop may suspend itself while you are working outside, so adjust its sleep setting or keep it connected where you can hear it. Test the volume once, then leave the browser running. If the browser is closed or the device sleeps, the alarm cannot sound, and the coconuts may still be exposed when the rain arrives.
While preparing the coconut area at midday, notice how the light changes under thickening clouds. Place the tarpaulin, rope, and weights where they remain easy to see even if the yard darkens before 2:44 pm. Avoid leaving ties in deep shade beneath trees or sacks. A nearby covered spot keeps everything visible and dry, letting you act on the alarm without searching through dim corners.