Torrential downpours brought flooding to parts of the country today, as firefighters in storm-hit areas admitted they were "stretched" amid a strike by union members.
A number of homes and roads were flooded in south-east England after the Met Office issued a "yellow" warning for rain across eastern Britain.
The Environment Agency issued two flood warnings, meaning flooding is expected, while more than 20 flood alerts were in place across the Midlands, Anglia and the south of England.
Essex Fire and Rescue Service said it dealt with incidents including a house fire following a lightning strike, people stranded in vehicles stuck in flood water, cables arcing and hedgerow fires.
It came as Fire Brigades Union members went on strike from 5pm to 7pm tonight.
A spokesman for Essex Fire and Rescue Service said: "Firefighters are dealing with numerous flood and weather related calls across the county following thunder, lightning and heavy downpours.
"Canvey is one area particularly affected but calls have also included Southend, Harlow, Aveley, Ongar and Corringham, and resources are stretched."
Essex Police said properties in Canvey Island were flooded, while roads were blocked by flood water in Southend, Rayleigh, Castle Point, Wickford and Ramsden Heath.
The force urged motorists to avoid unnecessary journeys and drive with caution.
Southend University Hospital's accident and emergency department was temporarily closed due to flooding, the BBC reported. A site manager at the hospital refused to comment.
Flooding near Billericay meant that trains were unable to run between Shenfield and Southend Victoria and also between Wickford and Southminster, Network Rail said.
Norfolk Fire and Rescue Service said it had also dealt with a number of flood-related calls.
The EA issued flood warnings for the River Roach, Prittle Brook and Eastwood Brook in Southend, Essex, and for Spixworth Beck from Horsham St Faith to Crostwick in Norfolk.
Meanwhile, the Lambeth Country Show at Brockwell Park in Brixton, south London, was abandoned after torrential rain.
On Twitter, organisers wrote: "Sadly, we have had to close the event. We thank you for coming this weekend but ask, could you leave the park in a sensible manner."
John Curtin, the EA's director of incident management and resilience, said: "As we've seen over the past two days, flooding can happen very quickly so we urge people to continue to check local weather forecasts and the Environment Agency website for flood risk information on a regular basis.
"We will continue monitoring the situation closely and supporting local authorities, who will respond to any reports of surface water flooding."
Temperatures are likely to soar again next week, with the mercury possibly topping 30C (86F) for a three-day spell from Wednesday.
But the heat is again likely to bring with it the risk of heavy showers and thunderstorms, especially in the South, on Wednesday and Thursday.
Gemma Prebble, a forecaster with MeteoGroup, said: "By Tuesday there will be highs of 28C (82.4F) in the South East and on Wednesday, Thursday and Friday it will possibly be up to 30C (86F) in the South East."
Essex Police said flood-hit residents in Canvey Island were suffering "further anguish" because some motorists were driving too quickly and causing waves of water to enter homes.
Supt Stuart Ashton said: "We have 4x4 vehicles on the island and are closing as many roads as possible, but the scale of the flooding is over a huge area.
"The fire brigade have four appliances and the Environment Agency are on scene. The water levels are falling and I urge residents to avoid car journeys for as long as possible to allow water to fall.
"Some irresponsible drivers are causing misery to residents as they drive too fast through flood water, which is causing further water to enter their homes.
"Slow down, observe road closures and be patient."