Weather and its Effects

Checking out the weather report is a daily activity for many of us. At the very least, we want to know how hot or cold it will get, or whether there will be rain or snow. Some of us live in places where severe weather can produce dangerous conditions -- flooding, tornados, blizzards or fogs, so we pay attention to weather related warnings. And these days, weather reports are getting more sophisticated, with pollen counts and particulates for allergy sufferers, and UV indices to tell you whether you need sunscreen.

Since weather affects us so constantly, I put together this page to help understand the science of weather. I am not much interested in weather forecasting, which is a very technical subject. This information is much more basic, about why weather "happens", what's going on in the atmosphere, what weather-related terms we see on TV really mean, how to read weather maps. It's mostly practical information, from a not very technical perspective.

Weather and Climate
Before we begin, let's differentiate between weather and climate. Weather is the state of your local atmosphere at any given time, in terms of such measurements as temperature, wind speed, air pressure, precipitation, etc. Weather is very specific - it's about a particular place at a particular time. It varies on a relatively small scale - for example, it could be raining in your area, while it's dry 10 miles away. It could be 72 degrees near your home, but only 65 degrees a few miles away. You could have a thunderstorm at 6 p.m. and have the sky clear by midnight.

So when we're talking about weather, we are talking about a relatively small area and a very specific time. Moving to a different area, or going forward in time quickly changes the weather. On the other hand, climate is about long term averages. It concerns the same things as weather -- measurements like temperature, pressure, rainfall, precipitation -- but these measurements are averaged over a long period. If you say "the