Summary

The dew point temperature often controls the minimum temperature at night. It is difficult for the temperature to drop below the dew point temperature, because dew or fog must form and latent heat energy is released by that process. When the dew point is high, a good dew point forecast can be essential to a good minimum temperature forecast.

Other factors include clouds and land characteristics. Thick clouds prevent radiation from reaching the surface, and they also prevent radiation from escaping into space. The diurnal temperature variation can be much reduced or even eliminated by sufficiently thick clouds. Land characteristics also affect the diurnal temperature range. Dry soil makes for wide swings in temperature; moist soil or water reduce the temperature range. Finally, the surfaces of cities store heat efficiently and produce higher local temperatures, particularly at night.

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