September milling wheat on Paris-based Euronext settled 1.50 euros, or 0.8pc, down at 176.75 euros ($199) a tonne.
Chicago wheat fell sharply as forecasts of rain eased concern about corn crops while hot weather was expected to keep US wheat harvesting moving.
Wheat markets had rebounded late last week after the US Department of Agriculture (USDA) made a steep cut to its world wheat production forecast, led by a significant reduction to output in top exporter Russia.
"Tensions in world wheat supply and renewed strength in US corn could return to neutralise harvest pressure, or rather each factor could in turn impact the wheat market over the coming weeks which look like being volatile," consultancy Agritel said in a note.
In France, a warm, dry spell was helping wheat harvesting progress, although the absence of rain in forecasts for the coming days was encouraging farmers to take their time, traders said.
Early results were continuing to show decent yields and mixed protein readings, they said.
In Germany, standard bread wheat with 12pc protein for September onwards delivery in Hamburg was offered for sale unchanged at 3.0 euros under Paris December. Buyers were seeking at least 4.5 euros under.
With harvesting only starting in early regions, the market was awaiting a clearer picture of the German crop.
Polish prices were mixed in the last week.
"Millers and feed compounders seem to be covered for the next couple of weeks and are waiting in a relaxed mood for selling pressure to develop as the new harvest arrives," one Polish trader said.
"This is also because of expectations that the harvest will start about two weeks earlier than expected due to the hot and dry weather in June."
Polish wheat with 12.5pc protein content wheat was quoted at 650-690 zloty a tonne (152.5-161.8 euros) depending on region for delivery from the new harvest, unchanged on the week.
Exporters were offering to buy 12.5pc protein wheat at 715 zloty for August delivery to port silos and sellers were seeking 720 zloty, 10 zloty down on the week.
Like German wheat, Polish supplies were facing export competition from cheaper Baltic and Black Sea origins.
"I cannot see any major ships in port lineups to load wheat in Poland," the Polish trader said.
Further north, Sweden's wheat harvest is expected to double in size this year in a recovery from heatwaves and drought last year, cooperative group Lantmannen said on Monday.