"At least 11 people died of rain-related incidents in the past 24 hours. Two died due to a house collapse while the rest died from lightning," a government official said in Lucknow, capital of northern Uttar Pradesh state.
At least 80 people have died in the state since the annual monsoon rains began tearing through parts of India earlier than usual.
Western Maharashtra state has also been badly hit with 74 deaths so far, mainly from lightning, while a few people drowned at sea.
In northern India, pre-monsoon torrential rains brought cheer Tuesday to sweltering cities but the heavy downpours also threw road and rail traffic into chaos.
Dozens of trains ran behind schedule and several flights in the capital New Delhi and other cities were diverted, officials said.
Rush-hour traffic snarls in waterlogged streets of New Delhi led to frayed tempers, but most of the city's 14 million residents welcomed the downpour which brought lower temperatures after searing heat.
The mercury dipped to 21.5 degrees Celsius (70 degrees Fahrenheit) but 79.6 milimetres (three inches) of rain in one hour overwhelmed New Delhi's poor drainage system.
"If they can't cope with one day's shower, we shudder to think what will happen when the monsoon comes," said R.P. Tandon, an engineer at the city's Delhi Transport Corp.
The weather office blamed the torrent on "atmospheric disturbances over northern Pakistan" and reiterated that the actual monsoon would be delayed and was unlikely to hit on June 29 in northern India, the country's rice and wheat bowl.
"Activity has weakened although the monsoon is vigorous over other parts of India and we think its onset across northern India will be delayed by a few days," a spokesman from the meteorological department told AFP in New Delhi.
In July 2005, hundreds of people perished when Maharashtra's state capital Mumbai was hit by record rainfall.
In northeastern Assam state, some 600,000 people were stranded in floods this month but the waters have begun to recede and people were returning home, officials said.
The monsoon hit India's Andaman archipelago May 18 and then swirled up the west coast states of Kerala, Maharashtra and Gujarat.
