You often hear meteorologists compare how we stand during the month for rainfall compared to average, or whether or not the temperature will be warmer or cooler than normal. These are all comparing different weather variables to what we call the climate normal. So what all goes into determining these normal values, or averages?
Scientists look back over a 30 year period at various official weather observation stations across the globe, including places here in Kansas. These climatologists will then take weather data from each day of those 30 years and calculate things such as average temperature, sky cover, precipitation, snow, frost and freeze dates, as well as growing degree days. New averages, or normals, are released every 10 years. We are currently waiting for the new climate normals to be released for 1991-2020, and have been using data from 1981-2010 for the past ten years to establish each day what would be “normal”.
Of course your daily temperature and rainfall won’t match what is normal for each day all the time as every year different weather patterns will determine what kind of weather will occur that particular day in the year. However, these climate normals are important when trying to get a general idea months in advance to determine temperature tends or when the rainy season tends to occur and how we as humans can best prepare for these changes.
Not only do we use these observations from land-based reporting stations, but oceanic data helps us determine steering weather patterns in the upper levels of the atmosphere that may be setting up during a particular season. For example, cooler than average sea surface temperatures off the western coast of South America led to a more active 2020 Atlantic hurricane season. This La Nina pattern, as it is commonly referred to, indicates that in Kansas during the winter months, we can expect warmer than average conditions and generally less precipitation. Compiling data from land and ocean based reporting stations are crucial in helping to determine a general average baseline from the past 30 years to help better forecast and understand future weather patterns and trends.