Weather is the specific condition of the atmosphere at any particular place at any moment in time. It is described in terms of such variables as temperature, cloudiness, sunshine, fog, frost, precipitation, humidity, atmospheric pressure and wind. In most places, weather can change from hour-to-hour, day-to-day, and season-to-season.
Climate is the average of the weather—and any patterns in the weather—for a particular region over a long time period, usually for at least 30 years. Weather is determined by factors that change rapidly; climate is determined by factors much slower to change, or that do not change at all. Typically, the main determinant of a region's climate is its position on the globe (its latitude), followed by factors such as elevation, proximity to the ocean, and the presence of ocean currents. A simple way of remembering the difference is that climate is what you expect (e.g. cold winters) and weather is what you get (e.g. a blizzard on a particular day). As climate is a long-term average of weather conditions, variations in it are much more slowly evident than changes in the weather, which can occur in timeframes of a few minutes.
Climate change can refer to change in the global climate or in regional climates. A range of variables can cause slow changes to climates anywhere on earth. Many of these factors are natural—for example, slight changes in the luminosity of the sun, subtle shifts to the earth's axis or orbit, or the gradual drifting of the continents over millions of years. The composition of the atmosphere is also a major factor affecting the climate over the whole world, because it can determine how much heat the earth retains through the greenhouse effect.