NBC News reported that a new study to be published shortly in Geophysical Research Letters shows that the drought which covered much of the US in 1934 was the worst in 1000 years, based on tree ring records from across the country from 1000 to 2005 as well as modern climate observations. The atmospheric pattern started with a strong ridge of high pressure similar to what was seen in winter 2013-14 in the western US, but was enhanced by dust storms across the middle part of the country, which helped prevent rain from developing. The 1934 drought extended across 72 percent of the western US, compared to 60 percent in the 2012 drought. Dust from the central US blew all the way to North Carolina and Florida in April and May 1934, which is before the official “Dust Bowl” term was even used. You can read the story here. The story indicates that the 1934 drought was 30 percent more severe than the next worst, which occurred in 1580 according to tree ring analysis.