The time it takes for clothes to dry outside depends on several factors, not just the temperature. Other variables such as humidity, wind speed, sunlight, fabric type, and the initial wetness of the clothes play significant roles in the drying process.
However, in general, warmer temperatures, like 20 degrees Celsius (68 degrees Fahrenheit), can aid in drying clothes faster compared to colder temperatures. Warmer air has higher moisture-holding capacity, which means it can absorb more water from the clothes, promoting faster evaporation.
If the weather is sunny and relatively low in humidity, clothes can dry within a few hours at 20 degrees Celsius. On the other hand, if it's overcast or the humidity is high, drying time will be prolonged, even at the same temperature. Windy conditions can also accelerate the drying process, as it helps to remove the moisture from the clothes' surface more effectively.
Keep in mind that heavier fabrics, like denim or thick towels, will take longer to dry than lighter materials, such as cotton t-shirts or lightweight synthetic fabrics.
Overall, it's challenging to provide an exact time frame without considering all the relevant factors. The best approach is to keep an eye on the clothes and check their dryness periodically.