This chapter helps us learn to plan our trips and venture into the field with confidence by understanding how and why specific weather patterns develop. It reviews the weather basics needed for successful nightscape sessions. The chapter explores the different types of cloud patterns we will encounter and what they mean. The chapter discusses humidity, dew point and the conditions that cause fog, dew, and frost to form. This information helps us recognize and interpret telltale signs to know what they portend. The chapter investigates a variety of atmospheric science phenomena that are of particular interest for landscape astrophotography, including rainbows, noctilucent clouds, lightning, crepuscular rays, ice halos, sundogs, ice pillars, and the green flash. The shape and texture of clouds are affected strongly by whether they are comprised of water droplets, ice crystals, or a combination of both.