Observation is fundamental to understanding weather: to ‘read the sky’ is to understand weather. In the next two chapters we explore how weather is observed, first from the surface and then from space. In the first half of this chapter we will see how instrumental observations of weather variables such as temperature and rainfall are made. The human eye is another valuable instrument for weather observation, particularly changes in cloudscapes. This chapter shows how our view of the sky can be ‘decoded’ to add to our understanding of the weather.