In A Nutshell
While they are used interchangeably by some people, there is a significant difference between the two terms. Weather is the atmospheric conditions over a short period of time, like a week; climate is those same atmospheric conditions but over a very long period of time.
The Whole Bushel
First appearing in A.D. 795, the term “weather” originally meant “air; sky; breeze; storm,” only changing slightly to its modern meaning of “condition of the atmosphere.” When we talk or hear about the weather today, we refer mainly to the way it affects humans, whether it’s the temperature, precipitation, or wind speed. We never hear about what the weather does to the ocean or the mountains, mainly because one isolated day isn’t going to make much of a difference to the ecosystem.
Weather is also the specific conditions of that day or week, e.g. snowstorms, tornadoes, etc. It is relatively impossible to predict what the weather is going to look like more than two weeks in advance because of the unpredictability of the atmosphere. The tools meteorologists use to predict the weather should sound familiar: Doppler radar, weather stations, and dropsondes, which are devices dropped from high altitudes to measure the weather.
Climate is the extremely long-range view of the weather, often in ranges from 30 years to a few hundred years. When we talk or hear about the climate, part of the conversation refers to how it affects humans, but most of the focus is on how it affects the planet as a whole, i.e. plant and animal life. Because of our intelligence and technology, it is much easier for us to adapt to a changing environment. But the other creatures on the planet have a much tougher time, which is why climate, especially climate change, refers to them mostly.
Climate also refers to the average weather for a region or the average length of the seasons. Most people can remember their parents or grandparents telling them: “I had to walk through snow up to my chest to get to school.” Because (at least here in the US) that is no longer the case, it’s plausible to say that the climate of the country has changed. Another difference between the two terms is that weather cannot be changed, but climate can.