The right temperature should stay within the care label limit and be compatible with the detergent and the soil level. The maximum allowed value does not mean you have to use it for every wash.
Going beyond the limits before choosing the temperature
Read the care labels on every item in the load: a durable fabric does not let you exceed another item’s limit. On labels that follow the GINETEX system, the number in the washtub symbol indicates a maximum in degrees Celsius; the bars also limit mechanical action. The care label interpretation brings both decisions together.
Then check the working range of the detergent and the stain treatment. A cold cycle needs a formulation and a sequence that can deal with that soil. Raising the temperature does not automatically make up for overloading or an incorrectly measured dose.
Cold and hot are not universal values
Tap Cold may use the water as it comes in, while another Cold setting may regulate it: confirm what your machine does. The supply water temperature changes depending on location and season. On a machine with heating, the selected number also does not necessarily describe every stage of the cycle.
If you need to compare units, use °F = °C × 9/5 + 32. For example, 30 °C is 86 °F and 40 °C is 104 °F. These are unit conversions, not washing recommendations.
Hygiene and stains require another check
A protein stain or a delicate finish may need a different pre-treatment than a hot wash. Check the product instructions, especially if it contains enzymes. When the goal is disinfection, use a documented hygienic procedure; a single temperature does not prove its effectiveness.
Choose the temperature together with the cycle and the product. If the items do not share a compatible treatment, separate the load.