In the past week, the drought spread moderately, but intensified significantly.
How serious is this drought in the U.S.?
The National Climatic Data Center's latest report says the U.S. has "the largest moderate to extreme drought area since the 1950s."
The U.S. Drought Monitor map released July 26 showed 64 per cent of the contiguous U.S. in moderate drought or worse and 46 per cent in severe drought or worse. It was the fourth consecutive week in which the new record was set for the total area of the country in drought.
However, the map only dates back to 1999. The U.S. government uses the map to make disaster determinations.
"In the Plains and Midwest states, crop losses mounted, ranchers liquidated herds, and trees continued to drop leaves and branches," the NDMC reports.
By July 25, the U.S. Department of Agriculture (USDA) had designated 1,369 counties across 31 states as disaster areas, the largest number in the agency's long history.
The USDA added 76 counties to their natural disaster list on Wednesday, making farmers and ranchers in those areas eligible for federal assistance.
The Drought Monitor forecast model for the week ahead does predict "scattered showers and thunderstorms to Great Plains and Midwest core drought area."
Where is the drought most serious?
The drought map shows that drought conditions are severe in the centre of the contiguous U.S., while the coastal areas and northern border states are better off.
Rain this past week brought some relief to hard hit regions in the northern and eastern Corn Belt, but it stayed dry in the western Corn Belt and much of the Great Plains.
“Not only the dryness but the heat is playing a big and important role," explained Brian Fuchs, a Drought Monitor author. "Even areas that have picked up rain are still suffering because of the heat.”
What is causing the drought?
This drought results from several converging factors.
A La Niña event in the tropical Pacific Ocean, with its cooler-than-average sea surface temperatures, is the key factor. La Niñas usually lead to dry conditions in parts of North America. This La Niña has begun to subside.
In the winter, snowfall was way below average and temperatures were milder, so the soil likely dried faster in the spring and early summer.
In the U.S., the first six months of 2012 were the warmest on record, with record heat waves in March and June.
Heat records continue to be smashed in July.
St. Louis, Mo., for example, has already set its annual record for the most days when the temperature matched or exceeded 105 F (40.56 C). July 25, with a record high of 107 F (42 C), was day 11. The previous record was set in the dust bowl year of 1934.
The role of climate change in this drought has not been determined, but climate scientists have predicted that droughts will become more frequent and intense as a result of global warming.
What's the drought situation in Canada?
Rainfall in most of southern and parts of eastern Ontario during the growing season has been 40 to 60 per cent below normal, according to CBC meteorologist Johanna Wagstaffe. Parts of the Maritmes and western Quebec have been similarly dry.
The Ottawa area has been particularly hard hit by the drought. A shortage of feed crops in the area is forcing livestock farmers to reduce their herds and put animals up for sale.
Gerald Rollins, the director of the Ontario Cattleman's Association, said the drought has stressed the fields, the cows, and the farmers.
Henry Van Ankum, chair of the Grain Farmers of Ontario, says the number of crops on the brink of failure across the province is between 50 and 60 per cent.
A stable, high pressure dome has been keeping the jet stream in northern Canada, contributing to the drought conditions in eastern Canada, as well as the central U.S., Wagstaffe explained.
All that may have changed in the last few days. "The multi-million-dollar rain came," David Phillips, Environment Canada's senior climatologist told CBC News. "We're seeing exactly the rain farmers were praying for, hoping for, begging for."
Phillips says the intense high pressure area has moved east and there is more rain in the forecast for southern and Eastern Ontario, although the Ottawa-area outlook is still dicey.
Environment Canada models are showing the entire country as warmer in August and drier than normal over most areas, but Phillips notes that the precipitation forecasts are difficult to get right.
What crops are most damaged by the drought?
Corn is the worst hit. This year, farmers planted the largest corn crop since 1937, leading to forecasts of a record harvest. Two months of drought and heat have made that seem like a distant memory.
The USDA's July 24 Weekly Weather and Crop Bulletin reports that the corn crop continues to deteriorate, with just 26 per cent of corn still in good to excellent condition. At the same time last year, that number was at 62 per cent.
In the Great Plains and the western Corn Belt, "crops withered under the relentless, record-setting temperatures," according to the Bulletin, which notes that this heat "could not have come at a worse time" for corn and soybeans, which are entering the reproductive stage of development.
Soybean crops rated good to excellent tumbled from 65 per cent on June 3 to 31 per cent in the latest Bulletin.
"The current corn and soybean ratings represent the lowest conditions at any time of year since 1988," according to the USDA.
What crops are expected to do well in 2012?
The peanut industry anticipates a bumper crop after drought in the peanut belt devastated harvests in 2011. The USDA reports that 67 per cent of the peanut crop was in good to excellent condition, compared to 30 per cent at the same time last year.
Flavours should be unusually concentrated in some crops. Hot peppers should be hotter and melons should be sweeter.
"Hot, dry conditions result in higher rates of photosynthesis, leading to higher concentrations of fruit sugars," Jim Nienhuis, a horticulturalist at the University of Wisconsin-Madison told Associated Press.
How does the 2012 drought compare to past droughts?
What distinguishes this drought is how it "came on board in a short time frame," Fuchs told CBC News. He is also a climatologist at the NDMC. In May, "for the most part, everything was fine."
Fuchs and his colleagues call this a flash drought, because it developed and intensified so quickly.
This year's drought reminds him of 1988, when drought affecting roughly the same area resulted in a costly natural disaster. Fuchs anticipates there will be a larger yield reduction in 2012 because "this one is hitting everyone harder," he said.
The 1950s drought was more serious because it lasted successive years. Drought had hit the U.S. even harder in the 1930s.
What caused the 1930s Dust Bowl?
"The 1930s drought was the major climatic event in the nation's history," according to Siegfried Schubert of NASA's Goddard Space Flight Center.
In 2004, Schubert and colleagues at NASA published the results of their research that showed that the major U.S. droughts of the 1900s, including the dust bowl, were linked to cooler than normal tropical Pacific Ocean surface water temperatures: La Niña. As in 2012, that created dry conditions over the Great Plains.
The mid-'30s also had unusually hot weather.
The Great Depression led to a huge drop in wheat prices, which led farmers to plant more fields in order to cover their costs. In 1931, the first year of the drought, Kansas, the top wheat-growing state, actually had a record wheat harvest, which would stand until the "miracle crop" of 1947.
More than five million acres of previous unplowed land was turned into farms between 1925 and 1930, using what was relatively new machinery.
"Rain follows the plough" was a saying back then, but the farming techniques of that era contributed to the drought by drying out the soil.
When the drought hit and the winds blew away the topsoil, the region turned into a dust bowl.
By 1935, Kansas had its second-smallest wheat crop of the 20th century. That year, government programs to change basic farming methods began. Summer fallow, crop rotation, strip plowing, shelterbelts and other techniques would help reverse some of the damage of past farming practices.
What's the likely result for crop prices and consumers?
U.S. food prices were already increasing more than the inflation rate before the drought, and most economists expect that to continue, but not so much that it ignites inflation pressures.
Corn and soy prices have been on a tear lately, hitting all-time highs last week. Rainfall this week caused prices to fall, especially for soybeans. Much of the corn crop is considered too far gone for new rain to make much difference, so the price drop was much smaller.
Weak consumer demand makes it difficult for food processors to pass on their increased costs. General Mills CEO Ken Powell told Reuters this month that "consumers should see generally stable prices."
The impact could be greater on the price of meat and dairy products. U.S. corn and soybeans are mostly used for animal feed as well as ethanol and cooking oil. Feed makes up nearly half the production costs for poultry and dairy producers.
Economists say it takes about six months for higher crop prices to reach supermarkets, because food processors have usually locked in their costs ahead of time.
Global production levels will also impact domestic prices.
What's the likely impact on U.S. farmers?
Reuters reports that "U.S. farmers face this drought in their strongest financial position in history," due to record high farm income in 2011, debt-to-asset ratios at all-time lows, record-high land values and rising producer prices.
Farmers who use irrigation will feel less impact, while the livestock and dairy sectors will be harder hit, due to higher feed prices. As well, the USDA rates more than half the U.S. pasture and range land as being in very poor or poor condition.
Livestock producers are likely to cull their herds before they are fully grown, and the increased supply could put temporary, downward pressure on meat and dairy products.
Farmers outside the drought-affected areas may get higher prices for their produce, but there's also a downside.
According to Lester Brown, author of Full Planet, Empty Plates: The New Geopolitics of Food Scarcity, "The world may be much closer to an unmanageable food shortage – replete with soaring food prices, spreading food unrest, and ultimately political instability – than most people realize."