The longest day of the year — known as summer solstice in technical parlance — falls on June 21 every year.
The longest day of the year began at 5.42am (sunrise) and end at 7.25pm (sunset).
According to met office, the temperature could soar to maximum 41 centigrade today in Karachi.
June 20 turned out to be the hottest day of 2015 with temperatures in some parts of Sindh nearing 50 degrees Celsius. The city of Jacobabad in northern Sindh had a high of 49 Celsius, Sibi in Balochistan 48 C, Nawabshah in interior Sindh 47 Celsius and Karachi also had its hottest day of the year at 44 C.