Motorists navigated leafy avenues as a short, sharp thunderstorm swept across Delhi-NCR on 13 May 2025, bringing light-to-moderate rain and a welcome dip in temperature. In anticipation, the India Meteorological Department (IMD) issued an Orange Alert for the capital, warning of rain, lightning and gusts that could peak near 60 km h^-1. Airlines advised travellers to monitor flight status as occasional diversions or delays were possible.

Historical Context: Rare May Storms

Although May is usually Delhi’s driest pre-monsoon month, 2025 has bucked the trend. Early-morning thunderstorms on Friday, 2 May 2025 dumped 77 mm of rain in about six hours—the capital’s second-highest single-day May total since 1901—and hurled gusts up to 74–80 km h^-1. The squall uprooted trees, killed four people in Najafgarh, and forced the delay or diversion of more than 500 flights at IGI Airport.

The all-time May record still belongs to 19 May 2021, when Cyclone Tauktae’s remnant low funnelled 119.3 mm of rain into the city of Delhi within 24 hours.

Why So Unseasonal? Western Disturbances & A Neutral Pacific

The 13 May shower was triggered by a western disturbance—an upper-air trough that increasingly lingers into late spring. Peer-reviewed analyses indicate that the subtropical jet is retreating northward more slowly, allowing such systems to intrude into May and June more often. Globally, the tropical Pacific had transitioned from a weak La Niña to ENSO-neutral conditions by mid-April 2025, so no strong El Niño/La Niña forcing was present.

Orange-Alert Safety Checklist

• Stay indoors unless essential; close windows and secure loose items.
• Avoid sheltering under trees, metal poles or temporary structures during thunder.
• Postpone swimming or boating; lightning can strike open water.
• Unplug sensitive electronics to protect against power surges.
• Keep a flashlight, charged phone and basic first-aid kit handy in case of outages.