The time it takes to heat up a cast iron skillet depends on various factors, including the heat source, the skillet's thickness, and the initial temperature of the skillet. Typically, it takes a cast iron skillet around 5 to 10 minutes to heat up thoroughly on a stovetop over medium to high heat.
Once the skillet reaches the desired temperature, it tends to retain that heat quite well due to its high thermal mass. The temperature may fluctuate slightly as you add or remove food, but it will generally remain hot and hold its heat for an extended period compared to other types of cookware.
It's worth noting that cast iron cookware can have hotspots, which means some areas of the skillet may be hotter than others. This is especially true if the skillet is not evenly heated or if it's not sitting flat on the cooking surface. To ensure even heating, it's a good idea to preheat the skillet gradually over medium heat, allowing it to warm up more evenly.
Additionally, it's essential to use oven mitts or handle covers when cooking with a heated cast iron skillet, as the entire pan, including the handle, can become extremely hot and cause burns if not handled with care.