On the surface this is a simple matter to define: ‘weather is what you get, …climate is what you expect’ ( http://www.nasa.gov/mission_pages/noaa-n/climate/climate_weather.html). Weather is what happens now; it is an immediate experience. Climate is what happens over space and time; it is an observation. By general consensus, climate is observed over 30 years, or longer.
An example of a weather change is a sudden thunderstorm on a sunny day. An example of climate change is the year on year warming of the polar regions, resulting in the melting of the polar ice caps.
However, the objection to the popular interchangeability of these two terms is more important than simply pedantry. There are two main reasons for this common misconception between weather and climate: the first is ignorance; the second is wilful misunderstanding, as with the recent media discourse surrounding the stranding of the MV Akademik Shokalskiy (see http://www.newstatesman.com/future-proof/2014/01/weather-and-climate-change-are-not-same-thing for a discussion of this).
This confusion between, or worse, obfuscation of weather and climate, strikes at the core of much of the media and everyday discussion about climate change denial. ‘Climate change is not real because…’: ‘we’re having a cold winter snap’; ‘it’s a miserable summer’s day today’ – that’s not climate change, that’s weather. And a climate change sceptic media can use weather events such as the trapping of the MV Akademik Shokalskiy as a way of reducing climate-related concern in the minds of a public already embracing climate change denial.