A survey among winegrowers in Burgundy suggested "a dip in yields of 20 to 27 per cent compared to the average", local industry association the Bourgogne Wine Board (BIVB) has said.
This would result in a harvest of between 1.1m and 1.2m hectolitres.
The BIVB has warned that because the situation has been so different from producer to producer, these are not concrete.
However, a significant, double-digit drop in yields is likely after "hiccups" in the weather including extreme frosts in April, freak weather and hailstorms in mid-May and "little respite from mildew" have drastically upset the 2016 growing season.
Other regions, such as the Loire Valley and Champagne, also suffered.
In July, Naked Wines estimated up to half the harvests in the chablis area of Burgundy alone were estimated to have been destroyed as a result of the weather.
A spokesperson for the BIVB said summer had been a "blessing, being very dry, sunny and warm", prompting an earlier harvest.
"The sun and heat enjoyed in August and September nonetheless raised the mood, but on the eve of the harvest, the various complications triggered by these events are making things tricky for producers," the BIVB said.