There might be sudden rain.
急な雨が降るかもしれない。
There might be a sudden downpour.
急な土砂降りがあるかもしれない。
「急な」は sudden を使うことで表現できます。
downpour は普通の雨よりも強い「土砂降り」のニュアンスがあります。
In order to warn someone that something might happen, in this case, it might rain suddenly, you can say:
It looks like it will rain at any moment.
'It looks like' - It appears as if, it is likely to, It may.
At any moment - suddenly, without warning,
This is a common phrase to show that something may happen without any warning, something unexpected.
Another common way of expressing this same idea is to say:
It's likely to rain any second.
'Any second' also means at any moment.
A moment is the same as a second.
I hope that helps!
なにかが起きるかもしれないことを警告するとき（この場合は雨が旧に降るかもしれないこと）
It looks like it will rain at any moment.
と言うことができます。
It looks like : 〜のように見える、〜するだろう、〜するかもしれない
At any moment : 急に、予想外に
これはいきなり予想外に何かが起きることを表す、よく使われるフレーズです。
また、同じことでもこんなふうに言うことができます。
It's likely to rain any second.
Any second とは、 at any moment と同じ意味です。
a second と a moment は同じ意味なのです。
参考になればうれしいです。
It might rain suddenly, take an umbrella just in case
It looks like it could rain any minute
Suddenly means for something to happen without warning so you would not be prepared for it happening so you might want to tell the person to take a umbrella just incase it rains suddenly
any minute means some time within the near future (very soon)
I can see a rainstorm brewing,make sure you are dressed properly.
It looks like its going to rain soon.Don't forget to take an umbrella with you.
"Don't be caught in the rain."
You are predicting that it might rain and the person should make sure are indoors when it does eventually begin.
"I can see a rainstorm brewing,make sure you are dressed properly."
You are warning them to make sure they are wearing their rain jackets and boots in anticipation of the rain that is to follow.
"It looks like its going to rain soon.Don't forget to take an umbrella with you."
You are reminding them to take an umbrella and you are warning them about the rain.
"Don't be caught in the rain."
①「雨に濡れないようにね」
これは、雨が降ることを予想して、もし雨が降ってきたら、室内にいるようにと注意を促しています。
"I can see a rainstorm brewing,make sure you are dressed properly."
②「暴風雨になりそうだ。（濡れないように）きちんとした格好をしなさいね」
もうすぐやってくるであろう雨を予期し、レインコートやレインブーツを着用するように忠告しています。
"It looks like its going to rain soon.Don't forget to take an umbrella with you."
③「もうすぐ雨が降って来そう。傘を持っていくの忘れないでね」
雨が降ることを忠告し、傘を持参するように念を押しています。
Its threatening to rain. Please carry an umbrella.
If you are going out, please dress up for rainy weather. It will rain according to the weather forecast.
It looks like it will start raining soon. Please don't forget your rain coat and umbrella.
The verb 'threatening' used in the first statement is the present participle tense of the verb to'threaten' which has several meanings, but, in this context, it means 'rain seems likely to fall'.
The expression 'please dress up for rainy weather' is a polite request to the other person to carry a rain coat and an umbrella, items that come in handy when it is raining,, since it will rain according to the weather forecast.
So, you may say:
Its threatening to rain. Please carry an umbrella.
or
If you are going out, please dress up for rainy weather. It will rain according to the weather forecast.
or
It looks like it will start raining soon. Please don't forget your rain coat and umbrella.
threatening'とは'threaten'の現在分詞形で、いくつか意味はありますが、この場合、雨がふりそうという意味になります。
'please dress up for rainy weather' とは、誰かに、天気予報を見る限り、レインコートや傘など雨が降った時に役立つものを忘れずにねと丁寧に伝えることができる表現です。
It's threatening to rain. Please carry an umbrella.
雨が降りそうです。傘を持って行ってください。
If you are going out, please dress up for rainy weather. It will rain according to the weather forecast.
外出するなら、雨の用意をしていってね。雨の予報だから。
It looks like it will start raining soon. Please don't forget your rain coat and umbrella.
雨が降り出しそう。レインコートと傘を忘れずに。
In Ireland we would use the expression 'looks like it might rain soon' the most.
We might recommend bringing a coat or an umbrella if going outside.
'You should bring a coat/umbrella'.
アイルランドでは、'Looks like it might rain soon'（すぐに雨が降ってきそうですね）という表現が最もよく使われます。
出掛けるなら、コートや傘を持っていくことを勧めるかもしれません。
'You should bring a coat/umbrella'.
（コート/傘を持って行った方がいいですよ）
You might want to bring a coat - it could start raining.
When you go out take an umbrella - I heard it might rain later.
It could rain later, you should take a coat.
'You might want to..." We use this expression to gently advise someone about something.
"I heard it might..." This construction is used when talking about something that you perhaps saw on TV, listened to on the radio, or were told about by someone.
"I heard it might be better to go by bus as the train's really slow."
"You should..." We use this form when advising someone about the best action to take.
"You should go to bed earlier and then you'll feel fresher in the morning."
'You might want to..." この表現は、誰かに優しくアドバイスするときに使います。
"I heard it might..." この文法は、テレビやラジオ、またはまた聞きしたことを話すときに使います。
例
"I heard it might be better to go by bus as the train's really slow."
電車がすっごく遅いからバスで言った方が良いと聞いたよ。
"You should..." その人がすべき方法や行動をアドバイスするときに使う形です。
"You should go to bed earlier and then you'll feel fresher in the morning."
明日すっきり起きられるように今日は早めに床に入った方が良いよ。
アメリカ合衆国 
イギリス 
南アフリカ 
アイルランド 
