The present disclosure provides methods to produce 5-(halomethyl)furfural, including 5-(chloromethyl)furfural, by acid-catalyzed conversion of C6 saccharides, including isomers thereof, polymers thereof, and certain derivatives thereof. The methods make use of acids with lower concentrations, and allows for conversion of sugars into 5-(halomethyl)furfural at higher temperatures and faster reaction or residence times.