PARIS, June 26 (Reuters) - Euronext wheat slid on Friday in step with Chicago as falling crude oil prices and advancing Northern Hemisphere harvests took attention away from a severe heatwave in Western Europe that kept maize on Euronext near contract highs.

September wheat BL2U6 on Paris-based Euronext was down 1.6% at €202.75 ($231.24) a metric ton at 1603 GMT, retreating further from Wednesday's four-week high of €210.75.

Chicago wheat Wv1 also dropped by around 1.5%. GRA/

Crude oil dropped around 4% as an upturn in traffic through the Strait of Hormuz eased supply fears. O/R

De-escalation in the Iran war has also allowed fertilizer shipments from the Gulf to resume, contributing to a pullback in prices for the crop nutrients.

Concerns over drought-diminished yields in U.S. wheat and heatwave damage in France were tempered by rapid harvest progress on both sides of the Atlantic and strong production prospects in the Black Sea export zone.

"Traders are balancing weather-related risks against the advancing Black Sea harvest, which continues to underpin bearish sentiment," British merchant Frontier Agriculture said in a note.

The International Grains Council on Thursday raised its forecast for 2026/27 global wheat production, supported by an upward revision for Russia.

In France, farmers had harvested 7% of the soft wheat crop by Monday, ahead of a five-year average of 1% for the period, farm office FranceAgriMer said.

Soft wheat conditions declined last week but 76% of the crop was still rated as good or excellent.

Traders are assessing the extent to which the week-long heatwave may hit wheat yields. Many now expect the crop to fall below last year's 33.4-million-ton crop, with some talking of a possible drop below the 30-million-ton mark.

However, crop concerns remained focused on maize, with the French agriculture ministry pointing to a potential 30% drop in production and growers fearing an even steeper decline.

On Euronext, November maize EMAX6 was 0.1% down at €221.00 a ton, hovering near a contract high of €224.75 from Wednesday.

Maize crop conditions deteriorated sharply last week to reach an eight-year low, FranceAgriMer's data showed.

The heatwave in France is set to subside this weekend but little rain is forecast for next week as maize enters the crucial pollination stage.amid

($1 = 0.8768 euros)