Rain in the national capital over the past few days has brought a slight improvement in its air quality index in the "moderate" category but fog and low visibility have affected schedules of at least 20 trains.

Moderate and dense fog is predicted over the city over the next three days, according to the India Meteorological Department (IMD).

Delhi’s maximum temperature was recorded at 20.6 degrees Celsius, which is three degrees lower than normal temperature for this time of the year and minimum temperature was recorded at 8.4 degrees Celsius, one notch lower than normal.

The air quality, which had improved slightly due to rain and hail storms over the past two days, is expected to deteriorate during the next few days, according to System of Air Quality and Weather Forecasting And Research (SAFAR) said.

The humidity in the region throughout the day will oscillate between 55 and 61 percent, the IMD said.

According to Skymet Weather, an active Western Disturbance over Jammu and Kashmir had induced a cyclonic circulation over Northwest Rajasthan. Both the systems were strong in nature and thus, resulted in widespread rain and thundershowers. However, it was an intense hailstorm that has caused major damage to the standing crop.

"At present, the crop was in standing stage and such intense weather activity can either destroy the crop completely or damage the quality. We are afraid that one of both might be the case this time," the weather forecasting agency added.