Delhi Heatwave: IMD Readings, Alerts And Forecasts Across Stations

Delhi's first citywide heatwave of the season, driven by dry northwesterly winds, saw several observatories exceed 40°C with elevated night-time temperatures. IMD forecasts a move towards cooler afternoons due to moisture-laden easterlies and potential thunderstorms, while air quality remains in the poor range. Forecasts indicate relief may come late April.

Delhi faced its first citywide heatwave of the season on Saturday, as the India Meteorological Department confirmed that four of the five key observatories crossed the heatwave threshold. Safdarjung, the base station for the city, reported a maximum of 42.8°C, which was 5.1 degrees above normal, prompting a yellow alert for hazardous weather.

The spike marked Safdarjung’s highest April maximum temperature in four years, last surpassed in late April 2022 when the same site recorded 43.5°C. Minimum temperatures stayed above seasonal norms as well, keeping nights uncomfortably warm and allowing heat to build through the day without relief from rain.

Delhi heatwave: IMD criteria, key weather stations and temperature data

IMD defines a heatwave when the maximum temperature crosses 40°C and is at least 4.5°C above the climatological normal, or when it touches 45°C regardless of the departure. For a citywide declaration in Delhi, at least two stations, including Safdarjung, must meet this benchmark on the same day.

On Saturday, that threshold was exceeded at most major Delhi observatories. The Ridge logged the highest maximum at 44.5°C, which was 6.1 degrees above normal. Lodhi Road registered 42.6°C, 5.6 degrees above normal, while Ayanagar touched 43.2°C, 4.8 degrees above normal. Palam recorded a maximum of 42.5°C.

Delhi heatwave: Consecutive hot days, IMD alert and changing wind patterns

IMD confirmed that heatwave conditions had persisted across Delhi for three straight days, even though this was only communicated officially on Friday after media questions on Thursday. "Heat wave conditions have been realised at many places over Delhi. This is the third consecutive day of heat wave realisation over Delhi region. These conditions are likely to continue till Sunday. Under the influence of setting in of lower tropospheric level easterly winds, maximum temperatures are likely to fall leading to abatement of heat wave conditions over the region from April 28," an IMD official said.

Building on this, IMD issued a yellow alert for Sunday, signalling continued heatwave or near-heatwave conditions. The department expects a shift in lower tropospheric winds from the current dry northwesterlies to more humid easterlies from April 27, which could trigger thunderstorms and slightly cooler afternoons over the region.

Delhi heatwave: Forecast for rain, thunderstorms and wind speeds

Forecasters anticipate that daytime temperatures in Delhi may drop by 2–4 degrees between April 27 and 28, depending on cloud cover and rainfall intensity. IMD’s daily bulletin stated: "Partly cloudy sky with possibility of thundery development with a spell of very light rain towards afternoon is expected on Monday. Sustained surface winds speed 30-40 kmph gusting to 50 kmph is also expected during the day."

Weather specialists expect these conditions, including gusty winds and intermittent thunder, to last till April 29 as part of typical pre-monsoon activity. The showers are likely to be patchy rather than widespread, with many neighbourhoods receiving only brief spells. Even after the heatwave eases, IMD projects that maximum temperatures will stay above the long-period average.

Delhi heatwave: Role of winds, regional weather systems and recent history

Meteorologists say the current Delhi heatwave is being driven mainly by dry northwesterly winds and strong solar heating over the plains, both common during early summer in northwest India. These conditions limit cloud formation and rainfall, allowing temperatures to climb rapidly and remain high through the afternoon.

Mahesh Palawat, vice chairman at Skymet Weather, linked potential relief to a developing system over Rajasthan. "No relief is likely until chances of some rainfall across northwest India from April 26 to 28. There could be a slight cooling effect. This is likely because of a cyclonic circulation developing over Rajasthan, with chances of rain over Punjab, Haryana and Delhi, among other places in northwest India."

IMD’s outlook broadly matches that assessment, attributing the expected moderation to the arrival of easterly winds which carry more moisture than the current westerlies. These winds are expected to help trigger isolated thunderstorms and light rain, especially during late afternoons and evenings, lowering maximum temperatures for a few days.

Delhi heatwave: Past April heatwave days and air quality impact

April heatwaves are not rare for the national capital. Delhi recorded three heatwave days between April 7 and 9 in 2023. April 2022 saw 11 heatwave days, while April 2017 recorded four such days and April 2016 had one, underlining the month’s tendency for intense early-summer heat.

Alongside the rising temperatures, Delhi’s air quality also deteriorated. The Central Pollution Control Board reported an air quality index of 243 on Saturday, up from 226 on Friday, placing both days in the “poor” category. The Centre’s Air Quality Early Warning System expects the AQI to remain in this range through Sunday.

Night-time conditions stayed warm, with Safdarjung recording a minimum of 25.2°C, 2.5 degrees above normal, and Palam reporting 26.8°C, which was 3.5 degrees above normal. No rainfall was observed at any station in the 24 hours ending 5:30 pm on Saturday, allowing both heat and pollutants to accumulate across the city.