Grain markets have been assessing the effects of scorching temperatures in western Europe, which included a record high of 45.9 degrees Celsius (114.6°F) in France.
Severe crop damage like that seen during a northern European drought last year is not expected but analysts do expect the heat to impact what had been very good harvest prospects in some regions.
In a weekly update, FranceAgriMer estimated that 75% of soft wheat - France's main cereal crop - was in good or excellent condition by Monday, down from 80% a week earlier although still above a year-earlier score of 73%.
Spring barley saw the sharpest deterioration among cereal crops, with the good/excellent rating losing 10 points to 76%, now level with the year-earlier rating.
For winter barley, FranceAgriMer rated 73% of crops as good/excellent, down from 75% from a week earlier.
Analysts had anticipated winter barley, usually the first major cereal crop to be harvested in France, would see limited heat stress because plants were already mature.
Some 22% of the winter barley area had been harvested, up from 1% a week earlier, although this was well below year-earlier harvest progress of 76%, FranceAgriMer said.
Wheat harvesting was also getting under way.
There had been some initial harvesting of soft wheat in southern France but that did not represent a measurable amount of the national crop, FranceAgriMer said.
For durum wheat, which is used to make pasta, 6% of the crop area had been harvested by July 1, compared with zero a week earlier and 7% in the same week last year.
Grain maize, which is not harvested until late summer or autumn, saw good/excellent ratings slip to 79% from 82% the previous week.
Part of the French maize crop is irrigated, which can offset the impact of hot, dry weather. But low water reserves have led some French regions to restrict water use for agriculture, which could affect maize growing conditions this summer.