Several other cities in the state also saw the mercury breach the 40 degrees mark.
According to the meteorological department, in the next 24 hours, showers are likely at isolated places.
Lucknow recored a maximum temperature of 41.6 degrees Celsius and a minimum of 24.3 degrees Celsius today, met officials said.
Several other cities also experienced hot weather conditions. The maximum temperature in Varanasi and Jhansi was 43.4 degrees Celsius today, while it was 43.2 degrees Celsius in Orai.
Etawah (43 degrees Celsius), Fatehgarh (42.6 degrees Celsius), Sultanpur (42.4 degrees Celsius), Rae Bareli (42 degrees Celsius), Ballia (41.5 degrees Celsius), Kanpur (40.9 degrees Celsius), Gorakhpur (40.8 degrees Celsius), Najibabad (40.5 degree Celsius), Bareilly (40.4 degrees Celsius), Basti (40 degrees Celsius), also reeled under intense heat.