Stephen Jones wrote:I think the difference between
It can rain at this time of year. -- a general statement referring to previous, present and future years
and
It could rain at this time of year. - a prediction referring to a future part of this year
gets us nearer the answer..
I have pointed out before, we have often confused TENSE with SENTENCE. A similarity happens here, unfortunately. Modal verb denotes merely a possibility. If the sentence implies a meaning, then it is the possibility of the meaning. As I exemplified,
the SENTENCE "You talk about my wife again and I must kill you" implies a threat, and the modal verb helps express the possibility of the threat.
Your explanation to the MODAL VERB can be word for word said again to the same SENTENCE without one:
It rains at this time of year. -- a general statement referring to previous, present and future years
What does it mean to you? It is the Sentence, not the Modal Verb, that does the implication. What happens in a court if we know that A did it, but we testify that B did it? How many times shall we repeat this again? As I have noted before, very often, as we think we are talking about TENSE, we are actually discussing about the SENTENCE.
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Stephen Jones wrote:I would accept It can rain at this time of year
but not
It can rain tonight.Wrong
I would say only It could rain tonight is correct.
We can say "It can rain any time" as a warning, why can't I say:
"Take an umbrella, it can rain tonight."
== Usually we say
It could rain tonight as a mild warning. But if I want to emphasize the possibility, I use CAN.
By the way, To Emil32, the modal verb in "Driving drunk can be dangerous" sounds more of an ability than a possibility, but it is rather subjective, I guess.
Shun