Firefighters tackling blazes at a school and a hotel within a few miles of each other believe they could have been started by lightning.
Around 55 emergency service members were called to Lytchett Minster School in Dorset shortly after 7am today, while dozens of other firefighters tackled the derelict Cliff House Hotel in the Boscombe area of Bournemouth.
In a third incident, 20 sheep died in a barn fire at Stalbridge, near Shaftesbury, this morning.
Lightning during storms in the county overnight was again suspected as the trigger for the blaze.
Christchurch Station Commander Dave Arundel, speaking from the scene of the school fire, said: "Many of the students and teachers have been here and seen the devastation and simply fallen to their knees to see their work and classrooms going up in flames."
In a cruel twist of fate, the school was only recently fully reopened after a £12 million rebuild following a fire in 2000.
Staff and pupils had been working in temporary buildings after the original school building was ravaged by the fire at the turn of the millennium.
Mr Arundel said he feared another rebuild would be necessary once the full impact of today's blaze is realised.
He said: "In my professional opinion, children and staff will not be able to return to this building.
"We are still working on it, so we don't know the full extent of the damage.
"We are waiting to see if any sections of the building have collapsed, but I don't believe it to be structurally sound.
"This is probably the largest school fire of its kind we've had to deal with.
"There are dozens of firefighters on scene, and they will be here for some considerable time yet."
The fire is believed to have started in the school roof, and then engulfed the whole of the first floor and part of the ground floor.
Mr Arundel added: "Initially, crews saw flames from the roof so we believe this to be a lightning strike.
"Firefighters forced entry wearing breathing apparatus, tackling the fire internally at first, but it quickly became clear that it was unsafe to do so, so we have been fighting the fire externally since then.
"Although it is a scene of devastation, it is also a big relief that it was not term time with students in the grounds or buildings."
Crews from Wiltshire, Hampshire, Somerset and Devon were called in to deal with the three incidents.
Around 60 sheep were led to safety following the barn blaze, while there were not believed to be any people inside the derelict hotel, near the seafront.