Pune: The city experienced its warmest May nights in at least 12 years this May, with the Shivajinagar observatory recording an average minimum temperature of 24.12°C — the highest for the month since 2015, showed India Meteorological Department (IMD) data.The previous record for the highest average minimum temperature in May was 23.9°C, set in 2018. Of the 11 Mays from 2015 to 2025, eight had average minimum temperatures below 23.5°C, underlining how exceptional this year’s figures were, an expert from the Vagaries of Weather blog said.Daytime temperatures were elevated too. The city recorded an average maximum of 37.9°C in May — the highest for the month since 2020. IMD’s 12-year dataset shows that May maximum temperatures have ranged between 35.2°C (2021) and 38.6°C (2020).An IMD official highlighted the risks posed by warmer nights. “Warm nights are of particular concern because they limit the body’s ability to recover from daytime heat stress. When minimum temperatures remain high, the urban heat burden effectively extends through the night, raising risks for the elderly, outdoor workers and those without access to cooling,” the official said.Independent weather forecaster Abhijit Modak attributed the elevated daytime temperatures to persistent anticyclonic conditions. “These conditions promoted subsidence warming and allowed hot, dry northerly to northwesterly winds to dominate for several days. As a result, maximum temperatures crossed the 41°C mark on multiple occasions,” he said.Modak, however, said such variations were not unusual. “Weather is dynamic in nature, and every year evolves differently depending on prevailing atmospheric conditions. Variations of around ±1°C in monthly averages are quite common within long-term climatological datasets,” he said.He contrasted the situation with May 2025, when frequent pre-monsoon thunderstorms and an early monsoon onset on May 26 helped suppress daytime temperatures, resulting in a lower monthly average.During night, the city recorded an average minimum of 24.1°C, about 1.2°C higher than the climatological normal of 22.9°C. “This was among the warmest May nights observed in at least the past decade. The main reason was the relative lack of widespread pre-monsoon rainfall activity compared to some previous years. Higher daytime temperatures combined with increased moisture during periods of overnight westerly flow limited nocturnal cooling,” Modak said.Additionally, partly cloudy skies on several nights curtailed radiational heat loss. Unlike clear and calm conditions that enable effective cooling, the combination of cloud cover, moisture and light winds kept temperatures elevated through the night, he added.May average minimum temperatures by year:2015: 22.7°C2016: 23.6°C2017: 23.3°C2018: 23.9°C2019: 22.4°C2020: 23.1°C2021: 22.7°C2022: 23.4°C2023: 22.7°C2024: 23.5°C2025: 22.7°C2026: 24.12°C