4 sentences

1. 夏天总是闷热而又潮湿。

   xià​tiān zǒng​shì mēn​rè ér yòu cháo​shī.

   Summer is always hot and humid.

   Source: Tatoeba

2. 阳光灼人，让人感到非常闷热。

   yáng​guāng zhuó​rén, ràng rén gǎn​dào fēi​cháng mēn​rè.

   The sun is scorching, making it feel very muggy.

   Source: Dong Chinese Dictionary

3. 天气一闷热，我的心情就不好。

   tiān​qì yī mēn​rè, wǒ de xīn​qíng jiù bù hǎo.

   Hot and humid weather puts me in a bad mood.

   Source: Tatoeba

4. 闷热的午后，天边传来了阵阵殷殷的雷声。

   mēn​rè de wǔ​hòu, tiān​biān chuán​lái le zhèn zhèn yǐn yǐn de léi​shēng.

   On a sultry afternoon, low rumbles of thunder rolled in from the horizon.

   Source: Dong Chinese Dictionary