Yellow alert: What does this warning from the IMD mean?

Delhi experienced its coldest day of the year so far on Sunday, November 19, recording a temperature of 3.1 degree Celsius. This is due to a cold wave that has swept over the capital and its neighbouring areas. The lowest temperature was recorded at the Safdarjung observatory which is agreed upon as the official marker for the state. The Indian Meteorological Department (IMD) has predicted these severe conditions to last in certain parts of Northwest India at least till December 21. For now, the weather department has issued a yellow alert for Delhi for two consecutive days. Here is all you need to know about this situation.  

What is a yellow alert? 
The IMD uses different colour-coded warnings to indicate the state of weather in a specific region. These warnings are universal in nature and are also issued in times of flood and rainfall. The colours include green, yellow, orange and red in the ascending order of severity. The yellow warning which has been issued for Delhi, implies severely bad weather. This comes after a brief analysis of the weather over a given period of time. It also gives a heads up to citizens to expect a change in the weather from bad to worse with potential disruption to usual activities and day-to-day life of citizens. Such a warning urges people to stay alert and take the necessary precautions.  

Where else has the yellow alert been issued? 
Apart from Delhi-NCR and the surrounding towns and villages, the IMD has extended the yellow alert to the state of Uttarakhand as well. This is due to the fact that certain regions in this state like Mussoorie, Ranichauri, etc. have recorded near-freezing temperatures. The state of Rajasthan has recorded weather conditions worse than these. So, the IMD has issued an orange alert to the state. 

What is the cause of the cold wave in northern India? 
The cold wave across North India is a result of the north-westerly winds. These winds blow from snow-covered Kashmir, Himachal Pradesh and Uttarakhand. Apart from their origin regions, they can affect places as far as Punjab, Haryana, Chandigarh and Rajasthan. The cold wave situation is expected to settle post December 21.