After going through the wettest day this year on Wednesday, Delhiites  woke up to a thick blanket of fog over the city on Thursday morning as part of the freak weather that has left everyone amazed.

Delhi recorded a minimum temperature of 15.8 degrees Celsius on Thursday morning, the lowest for May in at least 13 years.

The all-time low of 15.2 degrees Celsius – since the weather keeping started – was recorded on May 2, 1982.

Apart from heavy rains, temperatures have plunged by as much as 10 degrees in May which is a peak summer month when mercury soars to 39.5 degrees Celsius. The maximum temperature recorded on Wednesday fzell to 30.6 degrees Celsius while the minimum was as low as 20.1 degrees.

Weather department officials said high moisture content in the air, still wind conditions and a significant difference between the daytime and nighttime temperatures create conditions that are favourable for the formation of fog.

According to the IMD, shallow fog is when visibility is reduced between 501 and 1,000 metres.

The Safdarjung Observatory, Delhi’s primary weather station, recorded 30 mm of rainfall in 24 hours ending at 8.30 am on Thursday.

Humidity levels varied between 80 per cent and 100 per cent at most places in the city.

Another western disturbance is likely to affect northwest India starting May 5. Under its influence, cloudy skies and sporadic rain is predicted in the capital until May 7, an IMD official said.

The main reason for the unseasonal rain is the “Western Disturbance”, said Dr Naresh Kumar, Senior Scientist at IMD. The western cyclonic disturbances are low-pressure systems that originate over the Mediterranean Sea. Under the influence of subtropical westerly jet streams, these wind systems reach India and cause rainfall.

The maximum temperature is predicted to remain below 35 degrees Celsius until May 8.

The Met office has predicted below-normal maximum temperatures and fewer heatwave days in northwest India in May.