Dozens of firefighters tackled a huge blaze in a field of corn on Monday, as scorching temperatures left the countryside in tinder-dry conditions.
Fire crews have been called to a series of blazes in the open over the last few days.
On Wednesday, the Met Office extended its amber warning for extreme heat for much of England and Wales, so it is now in place from Sunday until the end of Tuesday, with the hot spell expected to peak on Monday or Tuesday. The warning covers most of North Yorkshire, and parts of Teesside, and says that the heat could cause health problems across the population, not just among people vulnerable to it, leading to potential serious illness or danger to life.
The heatwave is a result of high pressure and hot air flowing to the UK from the Continent.
Widespread disruption, including road closures and cancellations and delays to rail and air travel are also possible, as temperatures look set to soar into the mid-30s or above.
People are being warned of the dangers of swimming in unsupervised areas of open water to cool off, and told not to leave pets or children in parked cars even for short periods.
And there are concerns about the risks of wildfire, with visitors to the countryside and green spaces warned not to use barbecues; make sure cigarettes are properly put out and disposed of; and not leave litter such as glass bottles which could cause a fire to start.
Monday's fire led to dramatic scenes near the A61 at Hutton Bank, north of Ripon, as a field being combined caught fire, leading to a major response from the emergency services.
Police warned motorists to avoid the area as six fire crews worked with the farmer to tackle the blaze.
At one stage, the fire front was said to be 300m in length. The cause of the fire is not known.
Almost at the same time, crews from York, Northallerton and Colburn attended a large field fire measuring approximately 100 metres well alight at Dishforth. Fire fighters used pitchforks and beaters and a hose reel to extinguish the blaze.
On Tuesday evening, a fire broke out in straw bales on Gateforth Lane, Hambleton, near Selby, where a fire crew helped the farmer in moving the bales onto concrete, and assisted with damping down an adjacent crop. A short time later, a report of a fire in a field at Sudforth Lane, Selby turned out to be a smoking combine harvester. Crews liaised with the farmer to extinguish hot spots and dampened down the surrounding area.
Meanwhile on Wednesday, crews from Easingwold, Acomb, York and Huntington were called to a large field fire in Flawith.
In addition to the fire risks of the heatwave, which comes on top of prolonged periods of lower than average rainfall in some areas, water companies are urging households to be careful with their water use in the house and garden.
People are being encouraged to take shorter showers, swap the hose or sprinkler for a watering can and not to water plants when the sun is out; turn off the taps when cleaning their teeth and only put dishwashers and washing machines on when they have a full load.
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