At the start of Harry Potter and the Half Blood Prince Fudge explains the current events to the Muggle Prime Minister and among them a "hurricane" in the West Country (actually the damage was caused by a giant):
"So I suppose you're going to tell me he caused the hurricane in the West Country too?" said the Prime Minister, his temper rising with every pace he took. It was infuriating to discover the reason for all these terrible disasters and not to be able to tell the public, almost worse than it being the government's fault after all.
"That was no hurricane," said Fudge miserably.
"Excuse me!" barked the Prime Minister, now positively stamping up and down. "Trees uprooted, roofs ripped off, lampposts bent, horrible injuries--"
"It was the Death Eaters," said Fudge. "He-Who-Must-Not-Be-Named's followers. And... and we suspect giant involvement."
The Prime Minister stopped in his tracks as though he had hit an invisible wall. "What involvement?"
Fudge grimaced. "He used giants last time, when he wanted to go for the grand effect," he said. "The Office of Misinformation has been working around the clock, we've had teams of Obliviators out trying to modify the memories of all the Muggles who saw what really happened, we've got most of the Department for the Regulation and Control of Magical Creatures running around Somerset, but we can't find the giant--it's been a disaster."
How could the Ministry of Magic hide the fact there was a giant involved? If they explain it with a hurricane there are lots of issues with that:
- A hurricane that caused the described destruction would be a major event in the news.
- It would be a big surprise for the meteorologists all around the world - usually hurricanes occur under a certain conditions which most probably were not present at the moment of the giant attack.
- Since 1980 or so we have satellites photographing a lot of stuff. Local investigators might be fooled to skip the photos, but some suspicious scientist in the USA or China could just get the necessary information and see what happened. The photographs might not be precise enough to show the presence of a giant but will definitely show that there was no hurricane.
- We also know that magic has its limits - the most important one is eye contact. So it is not possible to just erase all the evidence for a certain event - for example the photo taken by a satellite and stored somewhere on the Internet.
All-in-all - in the information era it would be very hard to falsify the actual cause for such a level of destruction by just modifying the memories of the eyewitnesses.
How could the Ministry hide the facts in this case?