“God forbid we go a single day without it raining.”
Today you woke up to see that the sky is dark and it's raining again, as it has been all week. You're in a bad mood because you wanted to go out to play soccer with some friends today. You say this to yourself, sarcastically.
God forbid we go a single day without it raining.
"God forbid ___" is a way of saying "Please don't let ___ happen" or "I hope ___ doesn't happen". You can use this for things that you really don't want to happen:
Please remember to take your phone with you. God forbid something bad happens to you and you can't contact us.
However, there's another popular use of "God forbid". People often say this sarcastically, to talk about something that they really do want to happen, but which doesn't seem likely to happen. For example:
God forbid you get off the couch and help out around here! (talking to your lazy child)
We're having Thanksgiving at Millie's again this year, huh? God forbid we ever mix it up a little and have it at someone else's house.
When you use "God forbid" in this way, you sound angry and resentful. This is the way that the speaker used "God forbid" in the example at top.
Grammatically, notice that the part which follows "God forbid" is always in the simple present tense:
God forbid we go
God forbid something happens
God forbid we have it
You might also hear this phrase with "should":
God forbid we should go a single day without it raining.
The meaning is the same with "should" or without it.
This expression describes a period of time in which something doesn't happen.
You can't go all day without eating!
When I was younger, I went for eight years once without seeing a dentist.
In the example at top, "go a single day without it raining" means that there would be no rain for at least one day.
Saying "a single ___" isn't much different from just using "a" or "one". But "a single ___" emphasizes the point that you're talking about one thing, rather than more than one. It's mostly used in negative sentences, like "not a single ___":
I haven't made a single mistake all day.
We've never said a single word to each other.
But sometimes "a single ___" can be used in positive sentences with "even":
If we have the opportunity to save even a single life, we have to do it.
Please donate. Even a single dollar helps.
Although the example at top doesn't include the word "even", it falls into this category. You could include "even" in the sentence without changing its meaning:
God forbid we go even a single day without it raining.
When you're talking about weather, the construction "it is ___" is very common: