The minimum temperature in the city settled at 28 degrees Celsius on Tuesday, with a fresh spell of heatwave expected to sweep the national capital starting May 11.

The relative humidity at 8:30 AM on Tuesday stood at 61 per cent, according to data shared by the India Meteorological Department (IMD).

On Monday, the Safdarjung Observatory, Delhi's base station, recorded a maximum temperature of 40 degrees Celsius, a notch above normal for this time of the year.

The IMD has issued a yellow alert, warning of a fresh heatwave spell in Delhi which may see temperatures soaring to 44 degrees Celsius by Wednesday.

The heatwave spell may continue till May 15 as a mitigating weather system is unlikely to affect northwest India over the next one week, weather experts said on Monday.

The maximum temperature on Tuesday is likely to hover around 41 degrees Celsius.

The minimum and maximum temperature readings on Wednesday are likely to settle at 28 degrees Celsius and 44 degrees Celsius respectively with a heatwave forecast, according to IMD data.

The temperature in Delhi had started rising over the weekend and hit the 42-degree mark at some places on Sunday.

A heatwave in April-end had sent the maximum temperature soaring to 46 and 47 degrees Celsius in several parts of Delhi.

The air quality index (AQI) of Delhi was recorded in the moderate (151) category at 9:50 AM, data from CPCB showed.

An AQI between zero and 50 is considered good, 51 and 100 satisfactory, 101 and 200 moderate, 201 and 300 poor, 301 and 400 very poor, and 401 and 500 severe.