NAPERVILLE, Illinois, July 27 (Reuters) - Drought expanded last week across U.S. corn-growing areas, achieving the second-highest levels for late July in 24 years amid a cooler but drier week.

Next week’s data could show a worsening of drought conditions in the Corn Belt given this week’s sizzling temperatures and scattered rainfall, reigniting some crop concerns after what had largely been favorable July weather.

The U.S. Drought Monitor shows 59% of U.S. corn affected by moderate or worse drought as of Tuesday, up from 55% in the previous week, which was a six-week low. Some 23% of corn was experiencing severe or worse drought, up from 21%.

Those figures are significantly better than late July 2012’s moderate and severe drought coverage of 85% and 67%, respectively, though they are the week’s second-worst since 2000.

However, the share of corn areas under severe or worse drought is similar to some past years where yields were decent. That includes 2021, 2006 and 2005, where severe drought gripped 18-21% of U.S. corn in late July.

This same week in 2006 featured the largest moderate drought expanse in the Corn Belt after 2023 at 46% coverage, followed by 38% in 2005 and 36% in 2021.

Refinitiv data identifies those three years among the top 2023 Midwest weather analogs when considering the past 90 days of precipitation and 60 days of temperatures. 2005 and 2006 are overwhelmingly the best matches followed by 1989, 2021 and 2007. No other year since 1981 meets the similarity criteria.

The weather indexes do not discern the precipitation's timeliness, potentially weakening the argument for these analogs. But it is interesting that corn yields landed close to trend in those five years. Soybean yields varied more, though none were among the best or worst.

It is also worth noting that all five of the potential analogs featured above-average Midwestern rains in August, and four of them were warmer than normal. That suggests a switch back to wetter weather from here is more important for yield potential than a cool-down in temperatures.

Chicago grain futures eased on Thursday, partly on the expectation for favorable August weather. The U.S. government’s outlook on Thursday showed a mixed precipitation bias in the Corn Belt through Aug. 10.

SPRING WHEAT

Drought is creeping upward in U.S. spring wheat country with 43% of areas in moderate drought, the highest since March and up from 31% a week earlier. Some 4% of spring wheat is in severe drought, the first trace of severe drought since April.

However, spring wheat in top U.S. producer North Dakota has decent potential according to scouts on an annual crop tour, who pegged the state’s yield at 47.4 bushels per acre on Thursday.

That is down from 49.1 bpa on last year’s tour but better than the five-year tour average of 40.1 bpa, which includes a 29.1 from 2021.

North Dakota’s spring wheat yield reached a record 50 bpa in 2022 despite fears that delayed planting would be limiting. However, the state’s wheat had zero drought coverage a year ago compared with 44% this week.

The Department of Agriculture pegs North Dakota’s spring wheat yield at 47 bpa compared with 33.5 in 2021 and a string of 49s between 2018 and 2020. Refinitiv’s data suggests North Dakota’s best recent weather analog is 2012, which featured decent spring wheat yields in the state despite the drought’s devastation elsewhere. Karen Braun is a market analyst for Reuters. Views expressed above are her own.

(Reporting by Karen Braun Editing by Matthew Lewis)