As deadly fires continue to burn across bone-dry Texas and eight inches of rain from tropical storm Lee falls on New Orleans, the US is beginning to count the cost of nine months of unprecedented weather extremes.

Ever since a massive blizzard causing $2bn of damage paralysed cities from Chicago to the north-east in January, nearly every month has been marked by a $1b+-weather catastrophe. According to the National Oceanic and Atmospheric administration (Noaa), there have been 10 major disasters already this year, leaving more than 700 people dead and property damage of over $35bn (£22bn).

In the past 31 years the mainland states have suffered 99 weather-related disasters where overall damages and economic costs were over $1bn. This year has seen three times as many than as usual.

Noaa will release its August data next week but Summer 2011 is expected to be the warmest on record. Chris Burt, author and leading weather historian, has complied a list of more than 40 cities and towns that have experienced record temperatures this year.

"So many heat records of various types have been shattered this past summer that it is impossible to quantify them," he said. "Not since the great heat waves of 1934 and 1936 has the US seen so many heat-related records broken as occurred this summer. The back-to-back nature of the intensity of the past two summers should raise some interesting questions, questions I am not qualified to address."

This year, the UN World Meteorological Organisation said 2010 was the warmest year on record, confirming a "significant" long-term trend of global warming and producing exceptional weather variations.

The insurance company Munich Re said in the first six months of the year there were 98 natural disasters in the US, about double the average of the 1990s.

"The increasing impacts of natural disasters, as seen this year, are a stark reminder of the lives and livelihoods at risk. Severe weather represents a very real threat to public safety," said Jack Hayes, director of Noaa's National Weather Service.

But the US is not alone. 2011 has seen the deepest drought in 60 years in the Horn of Africa which has contributed to a famine in Somalia and 10 million people affected in Kenya, Djibouti, Ethiopia and Uganda. Southern Africa, however, experienced unusually heavy rainfall.

Latin America has suffered a series of disasters. More than 500 people died in some of Brazil's worst rainstorms and mudslides in January, and Columbia faced what it called its worst-ever natural disaster when months of rain and floods devastated the north of the country. Meanwhile Mexico and much of central America experienced one of their deepest droughts in many years.

Korea, the Philippines, parts of China have been racked with some of the worst storms in a century, with flash floods and landslides triggered by torrential rain .

2011 has also seen a series of major non-weather-related natural disasters. The worst, by some way, was the Japanese tsunami which killed at least 12,000 people and devastated the country. However, 6.2 or above earthquakes have hit New Zealand, the Philippines, Japan, the Fox Islands, Papua New Guinea, Mexico, Indonesia, Fiji, Thailand, Burma, Vanuatu, Argentina, Chile and Iran in the first six months of 2011. Smaller ones have hit Pakistan, Tajikistan, Tonga, and the Solomon Islands.

In addition the Arctic ice melt this year hit a record in July and is expected to the second or third greatest ever recorded, says the US national snow and ice data centre.

• This article was amended on 05 September 2011. The original stated the death toll for the Japanese tsunami was 1,200,000 instead of 12,000. This has been corrected

A year of US disasters – 2011 so far

• Hurricane Irene, August 20-29. Over $7bn and around 50 deaths.

• Upper Midwest flooding. The Missouri and Souris rivers overflowed in Montana, North Dakota, South Dakota, Nebraska, Iowa, Kansas and Missouri. Damages: $2bn.

• Mississippi river flooding, spring and summer. Damages neared $4bn.

• Drought and heatwave in Texas, Oklahoma. Over $5bn.

• Tornadoes in midwest and south-east in May kill 177 and cost more than $7bn in losses.

• Tornadoes in the Ohio Valley, south-east and midwest on April devastate the city of Tuscaloosa, kill 32 and cause more than $9bn in damages.

• Tornadoes hit from Oklahoma to Pennsylvania 14–16 April. Toll: $2bn in damages.

• 59 tornadoes in midwest and north-east April 8-11. Damages: $2.2bn.

• 46 tornadoes in central and southern states 4 and 5 April. Toll: $2.3bn in damages.

• Blizzard late January paralyse cities from Chicago to the north-east. Toll: 36 deaths and more than $2bn in damages.