May concluded with a remarkable heatwave, setting new records across Spain, as confirmed by the State Meteorological Agency (Aemet) and various data points. César Rodríguez Ballesteros, a climatologist, noted that May introduced three of the top ten hottest days for the month, with the highest temperatures occurring on May 29, 30, and 31. Specifically, Thursday's peak reached an average of 32.19°C, making it the warmest May day since records began in 1941, according to expert analysis.

Friday and Saturday followed closely, with averages of 32.13°C and 31.95°C respectively, ranking second and third among the hottest May days recorded. May 28 narrowly missed entering the top ten, securing the eleventh spot. Rubén del Campo, Aemet spokesperson, highlighted that these days were not only the hottest in May but throughout the entire spring season, surpassing any temperatures recorded in March or April.

May 2025 surpassed the previously hottest May months, as Aemet compared this intense heatwave to past extremes lasting ten days. Notably, the days from 2015 and 2022, with temperatures of 31.28°C and 31.13°C respectively, were dethroned.

Del Campo emphasized that nine out of the top ten hottest May days occurred in the 21st century, illustrating increased intensity and frequency of heatwaves compared to the past. This phenomenon is attributed to climate change, exacerbating extreme weather events, making them more frequent, severe, and prolonged.

Rodríguez Ballesteros noted record-breaking minimum temperatures during this heatwave, although the warmest night still remains May 21, 2022, with an average low of 15.94°C. The nights of May 30 and 31 recorded the second and third hottest nights with 15.68°C and 15.41°C respectively.

Temperatures soared between 5°C and 10°C above average across the country, exceeding the 95th percentile, particularly concerning maximum temperatures. Aemet, using a different methodology, identified May 30 and 31 as days with record-breaking average temperatures of 24.08°C and 23.91°C, surpassing the previously hottest day of May 21, 2022, at 23.76°C.

During the last three days of May, 13 monthly records for highs and lows were broken, including multiple instances in Cádiz, Badajoz, and Cáceres. Notably, on May 29, 30, and 31, Sevilla airport recorded over 40°C consecutively, an unprecedented event since data collection began in 1951.

Since the first occurrence in 2006, 71 instances of 40°C in May have been recorded across 14 provinces, with recent additions from Sevilla, Jaén, Córdoba, and others. Montoro, Córdoba, leads with six instances of reaching 40°C in May.

Del Campo dismissed claims of a cold spring, noting that while March was unusually cold, April was warm, and May's final week was exceptionally hot. Meteorological forecasts suggest a challenging summer ahead, likely warmer than usual, especially in the Mediterranean and archipelagos, with a 70% probability. While rainfall predictions remain uncertain, heatwaves are expected given the pattern of the past ten summers.