Weather forecast
Weatherman; Good evening ladies and gentlemen. Here is today’s weather forecast. It’s not very good; I’m afraid there’s a storm coming up.
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It’s not very good;
1- What does “it” refer to?
Does it refer to “weather”?
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I’m afraid there’s a storm coming up.
2-What does “coming up” mean here?
Thank you
It refers to the overall weather situation and ‘a storm coming up’ means that a storm is to be expected shortly.
A fun colloquialism is:
“I’m afraid there’s a storm a brewin’.”
The storm is building up or developing.
Thank you so much, Torsten 
Very nice.
Thank you so much, Arinker
Very nice.
‘It’ refers to the weather forecast.
Thank you so much, Anglophile
Very nice.
