The Met Office has already confirmed the arrival of monsoon. It said more rains may occur in many parts of the state for the next few days.
The schools reopened after a two-month-long summer break in Lucknow.
Lucknow received more than 27 mm rainfall since Sunday as a result the temperature plummeted by 7.4 degrees Celsius Monday, said a Met official.
Electricity supply to Lucknow has also improved as demand that had peeked in the past few weeks had come down, officials said.
"There were only minor faults in it and power supply remained by and large good," a power corporation official told IANS.
Advance of SW Monsoon 2014
Advance of SW Monsoon 2014.
Girls enjoying rains in Allahabad
Girls enjoying rains in Allahabad on Saturday.
Vehicles move at a road during rains
Vehicles move at a road during rains in Allahabad on Saturday.
Young boys playing a game of football in rains
Young boys playing a game of football in rains.
People wade through a waterlogged road
People wade through a waterlogged road after heavy rains.
Monsoon clouds hover over Nagaon
Monsoon clouds hover over Nagaon in Assam on Saturday.
All the parks in the city were full on Sunday and people were spotted dancing in the rain.
Monsoon was expected to arrive in Uttar Pradesh by June 16 but was delayed by a fortnight.
"Heavy to moderate rains will continue for the next two days before it takes a break again for a few days," said J.P. Gupta, regional met director.
Rains may occur in full force July 11 and 12. The sky will remain cloudy in between and temperature would be down, he said.
Meanwhile, Bahraich recorded 64.4 mm of rainfall since Sunday. Basti received 46.2 mm of rains, Kanpur 15.4 mm and Rae Bareli 290.2 mm, which is among the highest in the state.