Monday March 22, 2010, started like any ordinary early autumn day — it was warm, the sun was out, winds were light.

But something extraordinary was brewing in those seemingly calm skies and it had even the most experienced forecasters on edge.

Key points: The warning for Perth was issued just over an hour before the storm hit

The warning for Perth was issued just over an hour before the storm hit With $1.3 billion in claims, the 2010 storm was the costliest in WA history

With $1.3 billion in claims, the 2010 storm was the costliest in WA history UWA was extensively damaged, including historic Winthrop Hall

"[It was] a beautiful sunny day, but there was a nervous energy in the office, we were all looking at the meteorological data and we knew we had a loaded gun in the atmosphere," Bureau of Meteorology (BOM) senior meteorologist Andrew Burton recalled.

"Everything was set up for severe thunderstorms to happen and for them to come over the metropolitan area."

By peak hour, the sky had turned an eerie grey as clouds rolled in from the north, unleashing the fiercest storm to hit Perth in living memory.

The sky turned grey as a powerful front blew over the metropolitan area in 2010.

Winds reached up to 120 kilometres per hour, torrential rain flooded streets and hailstones of record size pelted the city, bringing traffic to a standstill.

Looking on in horror as cars smashed beyond repair

Luxury car dealerships in Osborne Park were right in the firing line of the biggest hailstones, 6 centimetres in diameter.

Lexus of Perth managing director David Jeary said there was little anyone could do but look on in horror.

Thousands of cars were written off by the huge hailstones that pelted Perth.

"The speed with which it hit, the way the sky changed colour — it took on a sort of green tinge — and then the ferocity with which the hailstones fell from the sky, they were the key things I remember," he said.

"Everyone was just in shock because they had never seen anything like it.

"And I think they felt a little bit helpless because, as much as you wanted to get the cars away from the storm, you couldn't go out in it — the hail was just too large."

A total of 118 cars were smashed in that one dealership alone.

Across Perth the damage to vehicles, homes and buildings, including schools and hospitals, was unprecedented and the clean up lengthy.

Even after 10 years, hail-damaged cars with their distinctive dimpled exteriors can be seen across Perth. ( ABC News: Liam Phillips )

Amid the chaos more than 100 people were evacuated from an apartment building at the base of Kings Park after a landslide flooded homes with a metre of mud.

It was the costliest natural disaster in the state's history, leading to more than $1.3 billion in claims, according to the Insurance Council of Australia.

A landslide outside a block of apartments below Kings Park forced the evacuation of all residents.

Historic UWA building hit hard

The storm maintained its intensity as it tracked south from Perth's northern suburbs, ploughing into the University of Western Australia with force.

No part of the Crawley campus was spared.

Enormous hailstones were responsible for much of the damage. ( ABC News: Andrew O'Connor )

"I remember the storm coming and then complete chaos when it hit," director of student life Chris Massey said.

"We didn't expect anything like what we got.

"We expected a storm, but when it starting hailing you literally had to run for cover.

"It was bedlam to start with and then after that it was picking up the pieces and seeing what damage had been done — we went from astonishment to a bit of sadness."

Students at UWA inspect the hail which swept across the entire campus. ( Esmeralda Rocha: User submitted )

The agricultural science glasshouses were shattered, obliterating up to a year's worth of research, and thousands of library books were destroyed by a mudslide.

The offices and laboratories at the Queen Elizabeth II Medical Centre had to be relocated, trees collapsed and staff and student cars were dented.

Historic stained glass smashed

But perhaps the most poignant reminder of the storm's wrath was the damage done to UWA's grand Winthrop Hall.

Holes were smashed in the historic stained glass windows of UWA's Winthrop Hall.

Eight of its north-facing stained glass windows, made in the UK in 1935, were destroyed by the mammoth hailstones.

"The windows had been there for a long time and I guess it was more symbolically sad," Mr Massey said.

"It symbolised the impact [the storm] had because that was the last place we expected damage to be done."

Replacement windows were sourced from a company in the United States, one of the last in the world still manufacturing cathedral glass.

It took about a year for the new glass windows, which weighed almost 800 kilograms in total, to be installed due to shipping delays in the US and floods in Queensland.

It took a year to replace the windows after they were extensively damaged. ( ABC News: Irena Ceranic )

A one-in-100-year storm

To the general public, the storm was as unexpected as it was severe, barrelling in with little notice during school pick-up and the afternoon commute home.

But Mr Burton, who was in charge of BOM's severe weather services that day, described the mood in the office as "adrenaline charged".

The sky turned green above Perth as the freak storm hit the city. ( Mateusz Nowacki: Audience submitted )

"For most of us in the building it was something that we hadn't seen before, but we knew from the data that we were looking at that this was going to be something more severe than we'd had in our career.

"It was certainly something like a one-in-100-year storm, no doubt."

The first severe thunderstorm warning was issued at 9:45am covering a broad area of the South West, but it did not pinpoint Perth as being under direct threat.

A warning specifically for Perth was issued just over an hour before the city's northern suburbs were struck.

"Unfortunately we saw that a lot of people weren't able to react in that amount of time," Mr Burton said.

The hail was so heavy it resembled snow on the ground and caused enormous damage. ( ABC News: Andrew O'Connor )

The unpredictable nature of thunderstorms, particularly in the warmer months, means there is usually little lead time to warn the public before an intense cell hits the city.

But 10 years on, social media is making it easier.

"We have a few extra tactics these days to try and raise the profile," Mr Burton said.

"We have the extra channels so we do try to get out on Twitter and Facebook, we try to get out the message through as many channels as we can and of course we rely on the media.

"We haven't seen a repeat of a storm like that in Perth since, thankfully, and I'm hoping that I don't see one in the rest of my career.