The structure “快要/快/就要/要……了” indicates that something is going to happen.
For example:
yào xià yǔ le 。
要下雨了。It's going to rain.
huǒ chē jiù yào lái le 。
火车就要来了。The train is coming.
diàn yǐnɡ kuài kāi shǐ le 。
电影快开始了。The movie is about to begin.
wǒ de shēnɡ rì kuài yào dào le 。
我的生日快要到了。My birthday is coming up.
If there is an adverbial of time in the sentence, then only“就要.....了”can be used.
For example:
mínɡ tiān zú qiú bǐ sài jiù yào kāi shǐ le 。
明天足球比赛就要开始了。The football match will start tomorrow.
xià ɡè xīnɡ qī wǒ men jiù yào kǎo shì le 。
下个星期我们就要考试了。We're going to have an exam next week.
mínɡ nián dà wèi jiù yào huí měi ɡuó le 。
明年大卫就要回美国了。David will go back to America next year.