Fried rice made from rice you cooked an hour ago comes out damp and clumped, sticking to itself and to the pan no matter how hot the wok gets. Fried rice made from rice that spent the night in the fridge comes out dry, separate, and lightly browned in that same pan, same heat, same oil.
The rice changed while it sat there. What changed it is a starch reaction, not a kitchen superstition, and it's the entire reason day-old rice fries instead of steaming.
Why fresh rice turns into a steamed clump
A cooked grain of rice is mostly water by weight, and its surface is still tacky with starch that gelatinized — swelled, then burst — while it cooked. Both of those are still true the moment it leaves the pot.
Drop it into a hot wok this way and the surface water doesn't get a chance to cook off. It flashes to steam instead, and that steam keeps gently cooking the grain rather than searing it. The starch left on the surface does the rest, gluing each grain to its neighbors until individual grains frying in oil become one damp mass steaming in its own vapor.
What a night in the fridge actually changes
Cooling doesn't just lower the rice's temperature. It runs the same starch reaction that thickens a chilled sauce and stales a loaf of bread — retrogradation, the starch molecules that swelled during cooking slowly re-bonding into a tighter structure as everything cools.
In a grain of rice, that re-bonding pulls water out of the swollen starch and pushes it toward the surface, where the dry air in a fridge carries it away. The grain that went in tacky and swollen comes out firmer at the edges and drier on the surface, not because it lost water evenly all the way through, but because its starch rearranged into a form that holds less of it right where a wok will touch it.
Dry grains are what let a wok actually fry them
A grain with almost no free water on its surface behaves completely differently in a hot pan. There's no film of moisture left to flash into steam and blanket the grain in vapor, so the oil and the metal underneath can push the surface past the temperature where browning happens instead of just cooking it through again. The grains are also no longer glued together by soft surface starch, so they separate and tumble past each other instead of matting into a sheet.
That's the actual difference between fried rice and rice that got reheated in a wok — not the pan, not the oil, and not the heat. The grain.
Getting there without waiting for actual leftovers
The fastest way to get rice into this state is to help the moisture leave faster than it would sitting in a covered pot.
Spread it out in a thin layer on a sheet pan instead of leaving it mounded — more surface exposed to air means faster evaporation and faster cooling, and it gets the rice into the fridge sooner rather than later. Cooking it a little leaner to start also helps: using less water than you would for rice you plan to eat plain gives it less internal moisture to shed before it's ready to fry.
Getting it cold quickly matters for more than texture. Cooked rice can carry Bacillus cereus spores that survive cooking, and if the rice sits between roughly 40°F and 140°F for more than about two hours, those spores can germinate and produce a toxin that reheating won't destroy. The same move that makes rice fry well — spreading it thin and refrigerating it promptly instead of letting it cool slowly on the counter — is also what keeps it safe to eat the next day.