A storm hits a temple, and the speaker is caught in it. The first image is the sound of rain falling on the temple trees, compared to words in the book of a blind beggar. It's a strange comparison, and it suggests something rich but hard to read: a patter you can hear but never quite make out, like text in the hands of someone who can't see it, yet who may know it by heart.
Then the poem drops from the sacred to the shabby. The outhouse, which the speaker says nearly made them sick, becomes the place where the storm is felt most closely. When thunder rolls, the whole building shivers from top to bottom. The speaker seems to be inside, sharing the shaking with the structure.
The mood is a mix of reverence and discomfort. The poem lets the grand and the grubby sit side by side, and the thunder treats them the same. There's a quiet humor in that, along with real awe at the storm's power.