Weather & Climate

An important distinction between the terms "weather" and "climate" is often misunderstood. Take a walk and notice the temperature, humidity, and wind direction. You are observing the weather. Weather happens at a specific location and time, and it changes from hour to hour and from day to day. Climate, however, is the accumulation of weather statistics taken over a long time period, and you need to gather a lot of weather data before you can determine the climate. Take summer in San Francisco as an example. San Francisco , on average, has a maximum daily temperature of 69 degrees F (20.5 degrees C) during July. This climate information, accumulated over the past thirty years of July weather, tells us what the average weather is like for that month. However, on any given day in July, the weather can be quite different, as tourists often discover when the cold fog rolls in under the Golden Gate Bridge . Climate is what you expect the weather to be, but, of course, on any given day the weather can be very different.