What is the weather forecast? VS. How is the weather forecast? I've just seen these questions asked in an English group and been curious. "What" VS. "How" is the weather? (I use "how") but "What" VS. "How" is the weather forecast? (I answered "How" but it is incorrect answer) If we use "the weather forecast", it has to change "How" to "What" ? Could you give me more details about these questions, please?
Both sentences are grammatical, but they normally mean completely different things.
1. What is the weather forecast?
This is asking for a prediction of the weather at some point in the future.
In other words:
Is it going to be warm, cold, dry, or wet tomorrow?
2. How is the weather forecast?
This is asking for the methods used by people who predict the weather.
In other words:
Can you tell me what charts and formulas are used by people who work in weather offices?
It's possible to interpret the second sentence in the same way as the first, but it would normally not be phrased that way if that were the intended meaning.
To make the other meaning clear while still using how, the question would instead be phrased similarly to one of the following sentences:
How is tomorrow's weather forecast looking?
How is the weather looking tomorrow?
In both sentences, the addition of looking alters the meaning of the sentence enough that it's clear it's not asking about methods of forecasting the weather.
To address a comment about forecast versus forecasted:
Forecast is both a verb and a noun. The more common interpretation of the second sentence (exactly as it's written) is its verb form. Not all verbs have to take -ed in their construction. This is one of them. Both How is the weather forecasted? and How is the weather forecast? are acceptable. If the sentence were talking about fish, a totally different verb form would be used: How are the fish caught?
Merriam-Webster says this:
Cast is an irregular verb, and the past tense remains cast, rather than casted. A number of people and usage guides advocate in favor of extending this to other verbs which are formed with -cast at the end, such as broadcast, forecast, and typecast. …
Although we give the uninflected -cast ending as the most common form for all the verbs ending with this, we also give the -ed ending for the past tense of the following words: broadcast, forecast, telecast, and simulcast. For the words miscast, recast, and typecast we do not list an -ed inflected form.
So, both forecasted and forecast are fine, but forecast is more common. However, it's a matter of preference.
How/What is the weather forecast?
Welcome to ELL.
I have heard people use both "How" and "What" when asking about the weather, but the phrasing of the sentences differ quite a bit.
How is the weather outside? How was the weather in NYC? How is the weather in ...?
Here, we are asking the person if the weather is warm, hot, sunny, cold, windy, rainy, stormy, or cloudy, etc. This is very straightforward. We don't use "what" in the construction/phrasing above.
With regards to using the term "forecast", the phrasing needs to be modified.
Cambridge dictionary defines forecast as "a statement of what is judged likely to happen in the future, especially in connection with a particular situation, or the expected weather conditions".
Collins dictionary defines it as "a statement of what is expected to happen in the future, especially in relation to a particular event or situation"
Any "forecast" is a prediction/estimate/finding made by someone (or a computer). We ask "What does the forecast say?" or "What does the report say?" And not "How does the report say?"
What is the weather forecast for Spain vs Brazil (meaning what does the forecast look like for the day of the match between Spain and Brazil)? What is the weather forecast for the week? What is the weather forecast for the trip?
Take a look at this link from Cambridge dictionary: weather forecast.
EDIT: One could also say "What is the weather like in NYC?" Surely, "what" can be used without having "forecast" there in the phrasing.
****A similar question in ELL, “What is the weather today?” or “How is the weather today?”, has some great answers just like Jason's.