The first temperature after the middle of summer at or below 32 degrees is known and categorized as the "first frost," whether or not frost is actually visible. For Fargo, the latest first frost on record was Oct. 24, 1994. For Grand Forks, the latest first frost was Oct. 27, 1963. It is possible those records could be broken this year as the pattern going forward looks generally warmer than average.
The weather has cooled from last week, and cooler weather is certainly likely before the end of the month, so this is not a forecast of a record. Rather, this is an observation that conditions could come together to keep us above freezing for some time. If upcoming cool waves combine with rainy, cloudy or even windy weather at night, temperatures could be held just above 32 even in a chilly air mass. It would certainly be notable and unprecedented if the first frost were to be delayed into November.