Overall, climatic conditions in December were not the best. Temperatures were pretty high during the month and precipitation, on average, was below needed. More heat means more evaporation, which accentuates the issue of lack of water, which certainly affected crops this year.
Still, the latter half of the month saw improvements, a trend that seems to be continuing in January. Temperature in these first couple of weeks have been a lot milder and, thus, beneficial for crops.
On top of lower temperatures, precipitation also improved. On average, a soybean plant needs ~8 mm/day of rainfall to thrive in the reproductive stages of its development.
For a lot of areas, this improvement may not bring higher yields, as the damage done was already irreversible by the time the weather started to turn better. However, for a lot of other areas, there is still time, and these improvements might stop national production from continuing to fall.