Farmers in Carrathool, Griffith, Hay, Leeton, Murrumbidgee and Narrandera are being asked to consider their local weather conditions when harvesting.
The risk of harvest ignitions increases as the weather gets warmer and drier.
"Using harvesting or farm machinery on days of increased risk can be very dangerous as any sparks in dry crops can start fires that spread very quickly," NSW RFS MIA District Superintendent Kevin Adams said.
"These fires have the potential to threaten property and also destroy millions of dollars' worth of crops."
Superintendent Adams said the weather forecast for Friday November 27 and Saturday November 28 meant farmers should be regularly stopping harvest and checking their grain harvesting guide and weather conditions before deciding to continue.
"In recent years, a number of substantial fires have been started by farm machinery being used in hot and windy conditions," he said.
"The NSW RFS appreciates the cooperation of farmers and machinery operators on days of heightened fire danger.
"A short period of down time until conditions ease will lower the risk of fires breaking out and can prevent a great deal of damage for farmers and their neighbours."
Grain harvesting guides are available at the MIA Fire Control Centre or online at www.rfs.nsw.gov.au/harvesting-guide.