Time series of warm spell events using climate indices (1961-2021) for the cities of Athens and Larissa. Data include the first and the last day of each warm spell, and aggregate statistics about its intensity. Warm spell days were detected using the climate indices CTX90pct and CTX95pct. According to the climate index CTX90pct [(Perkins & Alexander 2013)](https://doi.org/10.1175/JCLI-D-12-00383.1), a warm spell event occurs when the maximum temperature exceeds for at least 3 consecutive days its 90th percentile for the base period. The 90th percentile ...