How Evening Thunderstorms Form in Summer 277词｜中阶
夏天里，很多人都见过这样的天气：白天还是闷热得让人不想出门，到了傍晚，天色却突然暗下来，风一阵紧过一阵，没多久就雷声、闪电和大雨一起出现。它看上去像一场毫无预兆的"突然变脸"，其实，这场雷雨往往从白天最热的时候就已经开始准备了。今天这篇，就来看看傍晚雷雨是怎么形成的。
On many summer days, the air feels hot and heavy by late afternoon. Dark clouds gather, the wind changes, and a storm breaks out. The ground has been warming for hours. As it becomes warmer, warm, moist air rises more easily and begins the process that leads to a thunderstorm.
很多夏日的傍晚，空气会先变得又热又闷，随后乌云聚集、风向改变，一场雷雨突然到来。它之所以常发生在傍晚，是因为地面已经被太阳晒了几个小时。地面越热，附近温暖、潮湿的空气就越容易上升，雷雨的"准备工作"也就开始了。
Warm air is lighter than cool air, so it rises. As it moves upward, it cools and water vapor turns into tiny droplets. They form clouds. Strong rising air can make clouds grow very tall. Inside them, ice crystals, water drops, and moving air create the conditions for lightning, thunder, and heavy rain.
暖空气比冷空气轻，所以会往上升。它上升后逐渐冷却，水蒸气会凝结成很小的水滴，云也就慢慢形成了。如果上升气流足够强，云会在很短时间里长得很高。云层里的冰晶、水滴和空气不断运动，最后就可能形成闪电、雷声和强降雨。
单词知识卡 1
名称：build up
词性/释义：v. 逐渐积累；逐渐增强
文中意思：指热量、云层或压力一点点增加，为后面的变化做准备。
常见搭配：
heat builds up 热量逐渐积累
On hot days, heat can build up near the ground. 在炎热的日子里，热量会在近地面逐渐积累。
pressure builds up 压力逐渐增大
Before a storm, pressure can build up in the clouds. 暴风雨来临前，云层中的压力可能逐渐增大。
Evening is often the moment when the day's heat has built up the most. Weather also depends on humidity, wind, and larger weather systems. But on a hot, humid day, late afternoon can provide the extra energy a developing storm needs.
傍晚往往是一天热量积累得最明显的时候，但这并不表示每场夏季雷雨都会在日落前后出现。天气还会受到湿度、风和更大范围天气系统的影响。不过，在又热又潮湿的日子里，午后到傍晚确实更容易给正在形成的雷雨提供足够能量。
That is why a summer thunderstorm can feel so sudden. The sky may look calm at first, while warm air and moisture are already moving upward. By the time we notice the dark clouds, the process has often been going on for quite a while.
这也是夏季雷雨总让人觉得"来得突然"的原因。表面上，天空一开始可能还很平静；但温暖潮湿的空气其实已经在上升了。等我们看见乌云压下来时，云里的变化往往已经持续了一段时间。
单词知识卡 2
名称：humid
词性/释义：adj. 潮湿的；湿度大的
文中意思：指空气里水分很多，让人感到闷热，也更容易为雷雨提供水汽。
常见搭配：
hot and humid 又热又潮湿
The air feels hot and humid before the rain. 下雨前，空气会让人感觉又热又潮湿。
humid weather 潮湿天气
Humid weather can make a summer day feel warmer. 潮湿天气会让夏天显得更闷热。
A summer thunderstorm may look sudden, but it has been preparing in the sky all day. Heat, moisture, and rising air are all part of the same story.
夏天的一场雷雨，看起来像突然发生，其实已经在天空中准备了一整天。热量、水汽和上升的空气，都是同一个天气故事里的角色。
所以下次傍晚看到远处的乌云，不妨想一想：它不是刚刚出现的，而是白天的热量和水汽终于找到了释放的出口。天气里的很多变化，都是这样一点点积累，最后在某个时刻被我们看见。
每天和雷小喵读一点，让英语慢慢变成看世界的方式。