Most death and destruction inflicted by tornadoes in North America occurs during outbreaks—large-scale weather events that can last one to three days and span huge regions. The largest ever recorded happened in 2011. It spawned 363 tornadoes across the United States and Canada, killing more than 350 people and causing $11 billion in damage.

Now, a new study shows that the average number of tornadoes in these outbreaks has risen since 1954, and that the chance of extreme outbreaks —tornado factories like the one in 2011—has also increased.

The study's authors said they do not know what is driving the changes. "The science is still open," said lead author Michael Tippett, a climate and weather researcher at Columbia University's School of Applied Science and Engineering and Columbia's Data Science Institute. "It could be global warming, but our usual tools, the observational record and computer models, are not up to the task of answering this question yet." Tippett points out that many scientists expect the frequency of atmospheric conditions favorable to tornadoes to increase in a warmer climate—but even today, the right conditions don't guarantee a tornado will occur. In any case, he said, "When it comes to tornadoes, almost everything terrible that happens, happens in outbreaks. If outbreaks contain more tornadoes on average, then the likelihood they'll cause damage somewhere increases."

The results are expected to help insurance and reinsurance companies better understand the risks posed by outbreaks, which can also generate damaging hail and straight-line winds. Over the last 10 years, the industry has covered an average of $12.5 billion in insured losses each year, according to Willis Re, a global reinsurance advisor that helped sponsor the research. The article appears this week in the journal Nature Communications.

Heavy rains and hailstorms were recorded in Samai, Oman and in Saudi Arabia on March 1, 2016.

Here some pictures and videos of these anomalous weather events.

A heavy spring snowstorm hit the Moscow region last night. The unexpected weather conditions complicated the situation on Moscow roads and forced Domodedovo and Sheremetyevo airports to cancel more than a hundred flights.

Weather forecasters predict the strongest snowfall for the end of the week. According to Russia's meteorological service, such snowstorms occur in March once every 50 years.

The snowfall took Moscow's residents by surprise. Pedestrians heading to work are getting stuck in the snow, while many car owners have to dig their cars out of snow banks.

However, many people have not lost their sense of humor and shared their impressions on social networks.

Heavy rain in south eastern Brazil has caused a deadly landslide in São Sebastião, São Paulo State, and widespread flooding in the streets of Rio de Janeiro city, where some areas saw over 90mm of rain in 4 hours.

São Paulo

The heavy rain began to fall on 28 February 2016. Two people died after they were buried in a landslide in the Boicucanga neighbourhood of São Sebastião on 29 February. The landslide destroyed several homes, leaving at least 11 people homeless. A total of 27 people were evacuated.

Agência Brasil say that a total of 7 people have died in landslides in the state since December.

The heavy rain also caused surface flooding in Baixada Santista on the coast of São Paulo state. Local civil defence personnel were called in to help carry out some evacuations.

Environment Canada says a major winter storm is expected to sweep into parts of southern Ontario and southern Quebec on Tuesday, bringing heavy snow to some areas and freezing rain elsewhere.

Toronto, Hamilton, Montreal and Quebec City are under winter storm warnings. Windsor is under a snowfall warning, while Ottawa is under a winter storm watch.

Parts of Quebec including Montreal and Quebec City could get more than 30 centimetres of snow.

Environment Canada has issued a series of winter storm warnings and watches that cover a large swath of southern Ontario and southern Quebec.

The storm, travelling north from central United States, is expected to bring snow to southern Ontario on Tuesday afternoon and southern Quebec on Tuesday evening. Snow in Quebec will intensify overnight and continue Wednesday.

Environment Canada says drivers should be prepared for messy conditions.

"There may be a significant impact on rush hour traffic in urban areas," it says.

Two minors died after being struck by lightning at Kambowo village, the Kavango East Police confrmed on Thursday.

The lightning strike happened at around 18h00 on Wednesday at a homestead at Kambowo village. According to police sources the incident reportedly happened while the children were playing at home.

The deceased minors who died instantly after being struck by lightning were identified as six-year-old Tracy Shitoka Likoro and five-year-old Gloria Kantema.

The police mortuary services were called to the scene shortly after the fatal incident to collect the children's remains.

"The two bodies were transported to Rundu State Hospital mortuary," Chief Inspector Chrispin Mubebo, the acting regional crime investigations coordinator of Kavango East, confirmed.

Kambowo village is some 25 km east of Rundu along the Trans-Caprivi Highway in Rundu Rural Constituency of Kavango East Region.

Lightning killed three men and injured one in Lilongwe on Friday afternoon in the city's low density Area 43 where the four were working, Police confirmed.

Lilongwe Police identified the three as Wedson Nkhunumbu,37, of Magombo Village, T/A Champiti, Ntcheu; Douglas Kachuma, 38, of Kaunde Village, T/A Mlumbe in Zomba; and 22-year-old, Isaac Ngolombe, from Donda Village, T/A Chimoka in Lilongwe.

The police further identified the survivor as Enusu Pinto, 23 from Kanyenda Village, T/A Maganga in Salima.

Lilongwe Police spokesperson, Kingsley Dandaula, told Mana that the men met their fate as they were working on the foundations of a brick fence on a plot belonging to one of the residents of the area.

"Rain started pouring and before the four men could find shelter lightning struck them killing Nkhunumbu, Kachuma and Ngolombe on spot while Pinto lied unconscious," explained Dandaula.

Western Bureau:

The heavy rains that have been lashing section of St James since late Friday afternoon resulted in significant flooding in several sections of downtown Montego Bay and has left several houses in the newly constructed Port Bello Housing Scheme, near Cornwall Courts, under water.

"We have had reports of Creek Street, Dome Street and the Sign main road being under water at this time," Montego Bay's mayor, Councillor Glendon Harris, told The Gleaner shortly after 1 p.m.

"We have teams from the National Works Agency, the Police and the St James Fire Department out there monitoring the situation".

As a result of the number of flooded roadways across the western city, traffic was reduced to a snarl in some areas and came to a complete standstill in many other sections, creating a nightmare for motorists and pedestrians.

Heavy rainfall in Malaysia has caused the third wave of flooding in the state of Sarawak on the island of Borneo.

A torrential downpour that began early on Saturday 27 February caused severe flooding in and some landslides in the district of Serian. Other areas affected included Padawan, Penrissen and Bau-Lundu.

The state's capital city, Kuching, was also badly affected, with some streets under 70 cm of water at the peak of the floods.

Local media say that much as 300 mm of rain fell in Kuching in 24 hours between 27 and 28 February, 2016. The city's drainage system is designed for a maximum of 180 mm of rain and was unable to cope. However, much of the flood water had subsided by late morning of Sunday 28 February.

Durban was on Saturday counting the cost of a storm that left at least five people dead and a dozen injured.

The storm that ripped through the Durban area on Friday night delivered a deluge of rain and hail with strong winds that uprooted trees and collapsed walls.

One of those walls collapsed in Durban's Westville suburb, killing a 55-year-old man.

ER24 spokesman Werner Vermaak said paramedics on the scene were informed that the man, another adult and two teenagers went to inspect the wall before it collapsed.

"‎At this stage it is not clear if they suspected damage to the wall and thus went to investigate. The wall collapsed on the man and pinned him under the rubble and water for some time."