The weather is now hot, now cold.

天气忽而冷忽而热。

《新英汉大辞典》

What strange weather here -- now cold, now hot.

天气真是邪门儿， 一会儿冷一会儿热。

《新英汉大辞典》

The weather is now hot, now cold.; It is sometimes hot and sometimes cold.

天气时热时冷。

《新英汉大辞典》

They are now discovering strange, new species of plants, animals and organisms surviving near hot currents that come out of the ocean floor.

VOA: special.2009.01.13

It's hot, so Celsius right now, I think it's about 31 degrees.

很热，按摄氏度算的话，得有31度。

来自田纳西 - SpeakingMax英语口语达人

If you can interfere with any stage in RNA processing you can stop a gene from being expressed and this is a very hot topic in molecular biology now and human therapeutics.

如果你能干扰RNA加工的任何一个阶段,你就能阻止一段基因的表达,这也是当今分子生物学,和新型疗法中非常热门的话题

耶鲁公开课 - 生物医学工程探索课程节选

Even as these dark memories linger, though, Laos is poised to follow a path traveled by its neighbors Vietnam and Cambodia, both now hot spots of a different sort: on the tourism map.

FORBES: Asian Beauty

Almunia saved a penalty in Arsenal's 2-0 victory over Hull City and with Manchester United and Chelsea both dropping points this weekend, Arsenal are now hot on the heels of the top two.

CNN: Kroenke increases Arsenal stake

Fall is now the hot new time to release titles, thanks to its juxtaposition with Christmas.

FORBES: US Video Game Sales Fall 10 Percent in June