Delhi Weather Update, AQI: Delhi woke up to yet another polluted morning with capital's air quality standing in the 'Very Poor' category with an AQI (Air Quality Index) of 369. City's minimum temperature rose to double digits for the first time in 15 days on Friday, but the respite is predicted to end soon. The weatherman has predicted that dense fog and cold wave will return from New Year's Day.

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The relief from cold in north India can be attributed to a western disturbance, a weather system characterised by warm moist winds from the Middle East. With the western disturbance retreating by Saturday, cold wave and cold day conditions are predicted to wallop parts of Delhi in early January, meteorologists said.

The mercury will drop to eight degrees Celsius on New Year's Eve - Saturday, and further to four degrees Celsius by Monday (January 2). Dense fog and cold wave conditions are predicted in parts of Delhi from January 1 to 5, according to the IMD.

The India Meteorological Department (IMD) has said that icy winds from the Himalayas will bring the minimum temperature down by three to five degrees Celsius in the plains of northwest India. "Dense fog is likely to continue over the region during the next 4-5 days. A fresh cold wave spell is likely to commence over northwest India from January 1," it said in a statement.

On Friday, Delhi's primary weather station - Safdarjung observatory - recorded a minimum temperature of 10.7 degrees Celsius, four notches above the normal. It was also the highest minimum temperature this month. The maximum temperature settled at 22.8 degrees Celsius, a departure of 2 degrees Celsius from normal.

The mercury will drop to eight degrees Celsius on Saturday and further to four degrees Celsius by Monday (January 2). Dense fog and cold wave conditions are predicted in parts of Delhi from January 1 to 5, according to the IMD.

A cold day is when the minimum temperature is less than or equal to 10 degrees Celsius below normal and the maximum temperature is at least 4.5 degrees Celsius below normal. A severe cold day is when the maximum is 6.5 degrees Celsius or more below the normal.

According to the IMD, 'very dense' fog is when visibility is between 0 and 50 metres, 51 and 200 metres is 'dense', 201 and 500 metres 'moderate', and 501 and 1,000 metres 'shallow'.

In the plains, the meteorological office declares a cold wave if the minimum temperature dips to four degrees Celsius or when the minimum temperature is 10 degrees Celsius or below and is 4.5 notches below the normal.

A severe cold wave is when the minimum temperature dips to two degrees Celsius or the departure from the normal is more than 6.4 degrees Celsius.

Non-essential construction work banned in Delhi-NCR amid spike in air pollution

In view of a spike in air pollution, the Centre's air quality panel on Friday directed implementation of curbs under stage III of the Graded Response Action Plan (GRAP) in Delhi-NCR, including a ban on non-essential construction and demolition work.

Capital woke up to 'Very Poor' AQI (Air Quality Index) of 369.

Delhi's 24-hour average air quality index (AQI) stood at 399 on Friday.

An AQI between 201 and 300 is considered 'poor', 301 and 400 'very poor', and 401 and 500 'severe'.

The sub-committee on GRAP, at a review meeting, noted that the AQI is likely to slip into the severe category due to calm winds and stable atmospheric conditions.

It directed authorities in Delhi-NCR to invoke curbs under stage III of the anti-pollution plan with immediate effect.

GRAP is a set of anti-air pollution measures followed in the capital and its vicinity according to the severity of the situation.

It classifies the air quality in Delhi-NCR under four different stages: Stage I - 'Poor' (AQI 201-300); Stage II - 'Very Poor' (AQI 301-400); Stage III - 'Severe' (AQI 401-450); and Stage IV - 'Severe Plus' (AQI >450).

If the AQI is projected to reach the severe category, restrictive actions under Stage III are to be invoked at least three days in advance. These include a ban on non-essential construction and demolition, closure of stone crushers and mining activities in the region.

Non-polluting activities such as plumbing, carpentry, interior decoration and electrical works are allowed.

The next stage -- "Severe Plus" category or Stage IV -- includes steps like a ban on the entry of trucks into Delhi, allowing 50 per cent of staff to work from home in public, municipal and private offices,closure of educational institutions and the plying of vehicles on an odd-even basis, etc.