NAPERVILLE, Illinois, Dec 1 (Reuters) - Exceptionally hot and dry weather in Brazil’s leading soybean region persisted for a second consecutive month through November, maintaining yield concerns.

The crop-heavy northern section of Brazil’s top soy and corn state Mato Grosso experienced the driest October-November period in at least a quarter century. Two-month rainfall of about 163 mm (6.4 inches) is 47% below the period’s recent decade average.

Mato Grosso grows about 27% of Brazil’s soybeans and accounts for almost 30% of the country’s soybean export program, the world’s largest.

Dryness is not Mato Grosso’s only problem, as average temperatures during the last two months were about 3.5 degrees Celsius (6.3 degrees Fahrenheit) above normal across all soybean-producing regions of the state, significantly higher than anything observed in at least the last decade.

This combination of hot and dry weather has caused considerable crop stress, and some farmers there have abandoned their soybean fields to plant cotton instead.

Although October-November precipitation in Mato Grosso was about half normal levels, it was not unprecedented, as nearly the exact total was observed three years ago. In 2020-21, rainfall in the critical months of December and January was also markedly below average.

Mato Grosso’s 2021 soybean yields were close to average despite this rougher weather, though there are some differences versus this year to consider, including the lack of extreme temperatures three years ago.

In 2020, the state’s planting progress was about two weeks behind normal schedule as of early November. Although delays are usually concerning, it may have worked to the crop’s advantage in this case because it allowed for later development when precipitation amounts were greater.

December 2020 rainfall was about 30% below normal, but the amount, about 160 mm or over 6 inches, was double what had been received in November, potentially keeping the crop going.

This year, soybean planting in Mato Grosso was ahead of the average pace through late October, though the last 20% or so went in slowly due to the dryness. This could make an argument for any later planted or replanted beans in the state to thrive should December rains come through.

The delay in the 2020-21 soybean crop reduced Mato Grosso’s second corn yields since it pushed the sensitive development period back into a historically drier time frame. Mato Grosso accounts for two-thirds of all Brazilian corn shipments.

During the third week of November, precipitation forecast by the American (GFS) weather model was significantly closer to the actual weather in Brazil’s Center-West region versus the competitor European (EC) model.

EC precipitation forecasts for the region have been consistently wetter in recent weeks than the GFS, so recent rainfall in Mato Grosso has fallen short of expectations to some degree.

As of midday Friday, the EC was heavier on rainfall through the early days of December than the GFS, though if the EC amounts are realized, it could bring some measurable relief. Karen Braun is a market analyst for Reuters. Views expressed above are her own.