weather forecast - will/going to

[Lenka]

I was told that weather forecast is told with using WILL:
e.g. It will rain tomorrow.
Tomorrow's weather will be warm and sunny.

We can't say "Tomorrow's weather is going to be warm", can we? I read it in Headway...


If it's the truth that it's not possible to say "Tomorrow's weather is going to...", why is the sentence below right?

- 'What a beautiful day! Not a cloud in the sky!'
- 'Ah, but the weather forecast says it's going to rain." <= why not only WILL?

[rewboss]

It's not a strict rule, it's just that weather forecasters usually use "will", because that is how we normally make predictions. "Going to" is used to indicate that something is definitely going to happen (see, I had to use it there). Sometimes the meanings overlap, because if we say that something is going to happen, that is also a kind of prediction.

So it's normal for a weather forecaster to say, "It will rain...", but other forms are possible. In your example, the speaker is so sure that it is going to rain that he turns the weather forecaster's prediction into a certainty. "Going to" very often also indicates that we expect something to happen in the very near future, usually because we can see the evidence already. If you point to a sky full of black clouds, you're more likely to say, "It's going to rain," because it's almost 100% certain.

[Casiopea]

In addition, be going to is used to predict the future when we have already got some evidence that something is certain or likely to happen. When this evidence is not present, or at least is not as concrete, will tends to be used.

• It's going to rain later (I can see the clouds building up)
  
• I think it will rain later (It often does at this time of year)
  

Source: learnenglish.org.uk

. . . the weather forecast says it's going to rain.

[Lenka]

hmmm... thank you...

but I guess I'll have to learn it by reading, listening and speaking, as this grammar difference seems quite "limitless". Although I know all these rules, it's not that easy to recognize which one I should use...

Anyway, sentence 'Ah, but the weather forecast says it's going to rain' is right if we used "will" instead of "going to"?
I believe it is, I'd just like to ensure myself...

[Casiopea]

Lenka, you're welcome.

Both "will" and "going to" are used to predict the future, but "going to" adds further information. It expresses a plan or an intention. That is, the event is pre-determined.

a simple prediction about the weather
a. The weather forecast says it will rain tomorrow.
=> 'tomorrow' is in the future, so 'will rain'. Whether there's evidence or not is not important. "will" expresses an event that hasn't yet happened.

a pre-determined prediction about the weather
b. The weather forecast says it's going to rain tomorrow.
=> Evidence: the satellite map indicates rain.

Read more about how to express the future here: http://www.edufind.com/english/grammar/Tenses13.cfm

[Casiopea]

Originally Posted by Lenka

I'd just like to ensure myself...

Note,

assure, ensure: to make certain
[a] assure + person
[b] ensure that . . .

Suggested Correction
I would just like to make sure.

[Lenka]

Well, the forecast is always set up according to the satellite map, isn't it?
But OK, I can understand there is a small difference... I just can't feel it that much. You know, I can feel it well in this sentence now, but if you gave me another sentence and said:"now, fill in going to/will" I would perhaps fail....
Anyway, thank you very much - it really helps me to practise English like this!

as to assure, ensure and make sure... thank you for the note! I didn't know I can use ensure just with the object...
Can I also say "I would like to assure myself" instead of " would just like to make sure" or is it impossible?

[Casiopea]

Originally Posted by Lenka

Well, the forecast is always set up according to the satellite map, isn't it?

Right. I agree that "going to" is the better choice. But that's not to say everyday speakers wouldn't use "will". You see, "present evidence" - the key to using "going to" - is subjective: How much credence does a speaker place on the evidence present? Consider,

[1] It will rain tomorrow, so says the weather forcast. But it's often incorrect.
[2] It's going to rain tomorrow, so says my arthritis. And it's always right.

In short, what speakers say and what the grammar tells us they should say will differ, but given a test situation, "going to" suits the grammar here: "The weather forecast says [indicates] that it is going to rain."

Originally Posted by Lenka

Anyway, thank you very much - it really helps me to practise English like this!

You're most welcome, Lenka.

Originally Posted by Lenka

Can I also say "I would like to assure myself" instead of "would just like to make sure" or is it impossible?

Well, "assure" has semantic ties with "convince", so reflexive assure myself/convince myself sounds a wee bit awkward to my ears. It's more the case that, I would like to make certain, make sure that what I know is correct, not I would like to convince myself that what I know is correct. Do you see the difference?

All the best,

[Lenka]

Oh, you're really very nice, Casiopea

Now, I can understand both assure and will/going to...

[Casiopea]

You're most welcome, Lenka.