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The warm setting on a slow cooker looks like the easiest way to keep a second round of holiday leftovers hot. Two state university extension services say the cooker is the wrong place to do the reheating. Colorado State University Extension and Mississippi State University Extension both point home cooks to the stovetop, the oven or the microwave first. Mississippi State’s Janet Jolley explains why: slow cookers are not made to move food through the temperature danger zone quickly.
The advice is long-standing food safety guidance, not a new announcement. Colorado State marks its page as reviewed in October 2025, and Mississippi State last updated its story in August 2025.
What each extension page says about leftovers
Colorado State University Extension, in a slow cooker page credited to CSU Extension staff with FoodSmart Colorado, puts the rule in one sentence: “Do not reheat leftovers in a slow cooker or crockpot.”
Mississippi State University Extension goes a step further on wording. Its feature story, published January 31, 2022 and updated August 8, 2025, says that “leftovers should never be reheated in a slow cooker.” The story quotes Janet Jolley, an Extension family and consumer science agent in Marshall County.
Two other extension pages say the same thing. University of Maine Cooperative Extension, in an October 19, 2023 article by Extension Educator Kathy Savoie, says a slow cooker should not be used for reheating leftovers. University of Illinois Extension’s leftovers page says to never reheat foods in a slow cooker. It says to reheat on the stovetop or in the microwave and then transfer the food to a slow cooker to keep warm. That page shows no author or date.
These pages are general slow cooker and leftovers guides, so the rule is not tied to one dish or one holiday. It reads as covering whatever is left from a holiday table, including turkey, stuffing and gravy, as much as chili or soup.
Why a slow cooker is the wrong tool for reheating
The explanation comes from Jolley. “Slow cookers are not made to move food through the temperature danger zone quickly,” she said in the Mississippi State story.
Her example there was frozen food, which she said takes a long time to climb from 0 degrees to 140 degrees, giving bacteria plenty of time to multiply. She then applied the same reasoning to reheating, saying it is best to reheat foods on the stovetop or in the oven or microwave.
The temperatures on the pages frame the concern. The Mississippi State story says cold foods should be stored at or below 40 degrees. Colorado State describes the danger zone as running from 40°F to 140°F and says bacteria grow rapidly there. Applied to leftovers, which start in the refrigerator at 40°F or below, that reasoning points to a long climb through the danger zone.
Colorado State’s page also says the internal temperature drops 10 to 15 degrees each time the lid is raised, a point it makes about the cooking cycle.
Reheat to 165°F first, then hold at 140°F
The slow cooker is not banned from the leftovers routine. Colorado State’s page gives it a different job. Leftovers should be heated in the oven, microwave or on the stovetop until they reach 165°F, and only then added to the slow cooker, which should keep them at 140°F or above for serving.
The 165°F figure is not unique to extension pages. The CDC’s food safety prevention page, dated Nov. 24, 2025, lists 165°F as the safe internal temperature for leftovers and casseroles. It says a food thermometer should be used to confirm that microwaved food reaches that temperature.
That order of steps matters for a crowded holiday table. A microwave or stovetop can bring a bowl of stuffing or gravy to 165°F quickly, and the cooker then only has to do what it was designed for, which is holding heat.
What the warm setting is actually for
Jolley described the warm setting in narrow terms. “The warm setting is safe to use for four hours once the food is cooked,” she said. She added that it “will only keep the food warm and should not be used for cooking or reheating foods.”
The story also notes that the warm setting’s temperature varies by slow cooker, so food on that setting must stay above 140 degrees to remain safe. The four-hour figure is Mississippi State’s for food that has finished cooking. For reheated leftovers, Colorado State’s 140°F floor is the number to hold to.
Colorado State also covers the end of the meal. Its page says to refrigerate food within two hours after cooking has finished, and the CDC page gives the same two-hour window for cooked leftovers.
How this fits with the other leftovers rules
The slow cooker question sits alongside the storage rules that apply once the meal is over. The site’s earlier report on how long Thanksgiving leftovers last in the fridge covers the 3 to 4 day USDA window for turkey, stuffing and gravy.
A separate list of leftovers that carry higher food safety risk looks at which dishes deserve the most care before they are reheated at all.
Taken together, the extension guidance comes down to an order of operations. Refrigerate within two hours, reheat to 165°F with a method that heats fast, then use the slow cooker only to keep the food hot at 140°F or above.
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This article was produced with AI assistance and edited for accuracy against the sources linked above.
Image: Cary Bass – CC BY-SA 3.0/Wikimedia Commons