Final answer:
We cannot determine the specific day with a low temperature of 18°C without the correct data for Cloud City.
Step-by-step explanation:
To determine the day with a low temperature of 18°C, we need to look at the given data. Unfortunately, the provided data consists of the high temperatures for a different location and time period, which is not helpful for answering this question. Without the correct data for Cloud City, we cannot determine the specific day with a low temperature of 18°C.