Final answer:
A comma is not needed when a dependent clause follows an independent clause in a sentence. Therefore, the sentence should be: 'The weather was terrible when I went to Chicago'. The original sentence used the comma incorrectly.
Step-by-step explanation:
The comma in the sentence The weather was terrible, when I went to Chicago is not correct. In English grammar, when a dependent clause follows an independent clause, there should not be a comma separating them. So the correct sentence should be The weather was terrible when I went to Chicago. Using the comma makes it seem like there are two separate thoughts, when actually, 'when I went to Chicago' is giving more information about 'the weather was terrible'.
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