17 A Dangerous Weather Maker

Thunderstorms are dangerous because they can give off lightning. Snowstorms can tie up traffic and strand people. But tornadoes cause some of the worst weather of all.

Tornadoes are very strong columns of twisting air. They come out of rain clouds and form funnels. The funnels move along the ground, picking up anything in their path. Tornado winds can be over 300 miles an hour. Property damage can be terrible. Most of the world’s tornadoes are in the United States. The flat middle section of the country—the Great Plains—is where many strike. Spring is the most common time for tornadoes. But they hit in other seasons, too.

Tornadoes can be rated by the damage that their winds do. The worst tornadoes have winds between 261 and 318 miles an hour. They can lift a sturdy wooden house off its foundation. They can even carry cars through the air. Tornadoes don’t happen very often.

The worst tornado happened in March 1925. It went through three states—Missouri, Illinois, and Indiana. It killed about seven hundred people and injured over two thousand. In one small town, over two hundred people were killed. Many of the dead were school children.

If you hear that a tornado is coming, look for a safe place right away. If you are indoors, go to a basement. If you are outside, lie flat on the ground. Treat these storms with respect.

雷暴很危险，因为它们会产生闪电。暴风雪会导致交通瘫痪，使人滞留。但龙卷风造成的是最恶劣的天气之一。

龙卷风是非常强劲的旋转空气柱。它们从雨云中形成，呈漏斗状。漏斗沿着地面移动，沿途卷起任何东西。龙卷风的风速可达每小时300多英里，财产损失可能非常严重。世界上大多数龙卷风发生在美国，该国中部的平原地区——大平原——是龙卷风多发地带。春季是龙卷风最常见的发生时间，但其他季节也会出现。

龙卷风可以根据其风力造成的破坏程度分级。最严重的龙卷风风速在每小时261到318英里之间，它们可以将坚固的木屋从地基上掀起，甚至能把汽车卷到空中。龙卷风并不经常发生。

最严重的龙卷风发生在1925年3月，它穿过密苏里、伊利诺伊和印第安纳三个州，造成约700人死亡，2000多人受伤。在一个小镇上，有200多人丧生，其中许多是学童。

如果你听说龙卷风要来了，要立即寻找安全的地方。如果在室内，就去地下室；如果在室外，就平躺在地上。要对这些风暴保持敬畏。