September rain falls on the house.In the failing light, the old grandmother (1-2)
Well, if fall doesn't signal change to you, then we don't know what will. Weather, light, temperature. It's a time of change, for sure, but what that change will bring, we've got no clue about.
She thinks that her equinoctial tears (7)
The grandmother thinks change is somehow cosmically connected to the equinox. It's yet another example of a moment in the poem when the physical changes of the world around her reflect the mental changes going on within her.
were both foretold by the almanac, (9)
Well, we doubt the grandmother's right here, but her belief in the almanac's predictive powers does tell us a bit about her character. She's kind of old school, and probably hasn't changed much in terms of the way she goes about her business. Still, she'll be forced to change, if the almanac has anything to say about it.