For example, if you're on a ship in the middle of the ocean, you won't notice much of a difference between daytime temperatures and nighttime temperatures because the water doesn't heat up or cool off much during the day and the air doesn't absorb much radiation by itself. However, we won't be forecasting for any ships during this contest.
Coastal stations experience the same sort of effect, whenever the wind is right.
When the wind is onshore, the air reaching a coastal station has passed over lots of water and very little land. Its temperature will be close to the water temperature, whether it's daytime or nighttime. The dew point also tends to be close to the water temperature. Soil moisture Believe it or not, moist ground can have an effect similar to open water. Although moist ground can easily absorb radiation, some of the energy is taken up in evaporating water.