Behind a pot of ferns the wagging clock
Tells me the hour's word, the neural meaning
Flies on the shafted disk, declaims the morning
And tells the windy weather in the cock.
Some let me make you of the meadow's signs;
The signal grass that tells me all I know
Breaks with the wormy winter through the eye.
Some let me tell you of the raven's sins.
Especially when the October wind
(Some let me make you of autumnal spells,
The spider-tongued, and the loud hill of Wales)
With fists of turnips punishes the land,
Some let me make you of the heartless words.
The heart is drained that, spelling in the scurry
Of chemic blood, warned of the coming fury.
By the sea's side hear the dark-vowelled birds.
Here the ‘some let me make you’ mantra is the correlative (that is the ‘then’ to the ‘when’), whereas in the first stanza it was: ‘My busy heart… sheds blood.’ 
 That is to say: ‘When the autumn wind is up, [then] let me make you some of the heartless words.’ A desolating end to the sentence. For both tone & theme, one cannot help but recall the monumental  The Waste Land , by T.S. Eliot, which, if Thomas hadn’t read, he would not have been considered a serious poet. 
 The injunction to let the audience be shown/told an awful thing in a deathly, desolate place is reminiscent of the poem’s most famous lines: 
 And I will show you  some thing different from either Your shadow at  morning  striding behind you Or your shadow at evening rising to meet you 
 I will show you fear in a handful of dust .
Especially when the October wind