This winter has not been kind to those living in temperate climates. From the Midwestern United States to Central Europe, snow and bitter cold have thrown a monkey wrench into the cogs of expectations.

Earth scientists call those expectations climate. At first glance it might appear that this icy climate has turned against current global trends. Rather, weather has found extremes within the expectations of climate.

We must be careful not to confuse climate and weather. They are related but the distinction is not trivial.

Climate is a composite of weather over time, but it is more than that. Climate encompasses the full range and extent of weather over time and not merely the averages. It is not possible to determine whether climate is changing based upon any single period. Climatic data reflect 30 years of weather, but smooth out extremes. When we experience an extreme weather event, it is difficult to determine whether it falls outside the parameters of the climate without looking at the details of the data.

In the same way that we cannot roll the dice only a few times to determine whether they are crooked, we cannot determine changes in climate by looking at the weather for a few years. By contrast, weather is the state of the atmosphere at a given time and place using certain variables that we have learned to measure. Most commonly, these are insolation, temperature, precipitation, humidity, clouds and wind.

Climates range in size scale from the soil of a high spot in the yard to planet Earth as a whole and every size in between. We measure and keep records about weather, but there are weather stations at only a relatively few sites around the planet. Within any given climate, there is always a wide range of weather conditions, which may be small as in a tropical rainforest, or large as in a temperate boreal forest. We can keep track of the highest and lowest high temperatures, for instance, and the lowest and highest low temperatures for a given day of the year.

It is impossible to visualize patterns in large tables of data, so we compact the process by calculating averages. In so doing we lose the details. The average monthly highs and lows that give the traveler help in deciding what kind of clothes to pack for a trip obscure the details but are only one aspect of the climate of a particular locale.

To know whether a particular weather event is normal for the climate in which it occurs, we need to look at the details of extremes of past events. Even if storms such as the ones that ravaged the eastern U.S. in January fell outside of past extremes, these new extremes will be incorporated into the data and by themselves will have little impact on the norms established by the 30-year record.

Climate is a man-made concept designed to guide our expectations, while weather is a measurable physical state.

Climate is what you expect; weather is what you get, expected or otherwise.

Richard Brill is a professor of science at Honolulu Community College. His column runs on the first and third Friday of the month. Email questions and comments to brill@hawaii.edu.