From Glossary of Meteorology
It includes recording, at least once daily, one or more of the following: maximum temperature, minimum temperature, and total precipitation since the previous observation; and may also include description of the weather (cloudy, clear, etc.) and atmospheric phenomena. Such observations compose the bulk of climatological data in the United States and over much of the world. In addition, meteorological observations are, of course, "climatological" inasmuch as they are used to derive climatological data.