Soybean futures rose to the highest since July in Chicago as hot weather grips the US growing region, raising concerns about crops.

Parts of states including Iowa, Illinois and Nebraska — large corn and soy growers — are under excessive heat warnings, the National Weather Service website showed Monday. While it can be notoriously hot from mid- to late August, temperatures for the areas are expected to break numerous daily and potentially monthly records, it said.

The “heat dome” could last for more than a week and is boosting crop prices, Paris-based adviser Agritel said in a note. The weather is a particular concern for soybeans, as they are still in a crucial development phase — while most corn has finished pollinating.

Traders will get a clearer view on yield potential as the Pro Farmer Crop Tour gets underway in the US this week, where scouts will check fields across the Midwest. Crop conditions had improved in recent weeks as rain reached the growing belt, curbing drought seen earlier in the summer.

Meanwhile, wheat futures fell, reversing earlier gains. The Financial Times reported that Ukraine could finalize a deal with global insurers as early as next month to cover grain ships sailing to and from its Black Sea ports. That comes after Russia exited the Ukraine grain deal in July.

--With assistance from Keira Wright.