Climatology is all about the patterns in weather: how quantities like temperature and rainfall change from month to month, from year to year or from place to place. The Climdex indices can help us understand those patterns.

What are extremes indices?

The indices calculated by Climdex are annual statistics of weather. They answer questions like:

As well as being calculated over the full year, many indices are available for a given month—he hottest day each January, for example.

Climdex offers 27 indices, all derived from daily temperature and precipitation data. These indices are a standardised set recommended by the World Climate Research programme. The standardisation of these indices allows researchers to compare results across time periods, regions and source datasets.

How are the indices calculated?

The Climdex indices can be calculated from any source of daily weather data—from weather station observations, from gridded reanalysis datasets, or even from climate models. We've already calculated the indices for several observation datasets, and we provide software to help you calculate the indices for your own weather data.