Police closed the A68 in both directions after a storm hit the Rowley Bridge area near Consett, County Durham, causing part of the bridge to collapse.
Debris fell on to a house undergoing renovation, trapping one workman inside the building for a short time, but no injuries have been reported.
For Wednesday evening Met Office severe weather warnings of heavy rain remained in place for Yorkshire and Humber, north-west and north-east England, south-west Scotland and the Borders.
The Met Office issued a severe weather warning for parts of south-west England and said there was a "moderate risk" of severe weather in much of Wales during Thursday.
Heavy, thundery rain is expected to spread north east during the day, with some downpours generating 25 to 50mm of rainfall.
Drivers were advised to take extra care and seek advice on traffic disruption on Thursday.
Meanwhile heatwave warnings in London and the South East reached Level 3 - the second-highest level - on Wednesday, with temperatures exceeding 30C and forecast to continue through Thursday.
The Department of Health has issued special advice for the elderly and other people at risk from the heat.
It is the first time the Met Office has issued a Level 3 heatwave alert since June 2006.
It occurs when temperatures reach a certain threshold - which varies by region - and are sustained in one or more regions over two nights and the intervening day, with a forecast of higher temperatures to come.
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The Met Office said a key factor in raising the alert had been night-time temperatures, with some areas not falling below 18C.
The highest heatwave level - Level 4 - is classed as "red emergency".
It is reached when heat is so severe that illness and death may occur among the fit and healthy, and not just in high-risk groups.
Met Office spokeswoman Sarah Holland said temperatures in London and the South East could reach 33C on Thursday.
The most up-to-date figures for the government's health advice line NHS Direct show it took 318 calls from members of the public on Tuesday, complaining about sunburn, heat-exhaustion, breathing difficulties and other heat-related ailments.
The Department of Health (DoH) said those at most risk from heatstroke included the very young and the very old, and people with heart and respiratory problems.
It said people should contact their local environmental health officer if they had concerns about living conditions for themselves or a vulnerable friend, neighbour or relative.
Debris fell on a house undergoing construction work
London Underground passengers are being advised to take bottles of water on every Tube journey.
And St John's Ambulance volunteers are on hand to issue advice and treat tennis fans suffering from the heat at Wimbledon.
The London Ambulance Service urged people to only call for an ambulance in a genuine emergency.
It has been treating large numbers of patients for breathing problems, chest pains, loss of consciousness and fainting. The service received 4,765 calls on Tuesday - an increase of 21% on the previous week.
What is the weather like where you are? How will you be coping with the soaring temperatures? Will you be going to the beach or sweating in the office? We want to see how you will be staying cool.
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