Cambridge Discovery Education Interactive Readers are the next generation of graded readers - captivating topics, high-impact video, and interactive exercises designed to motivate and engage. What does the word `hot` mean? From the Sahara Desert to heatstroke, from temperature to emotions, learn how heat affects our world. Use the unique code inside the book to access the online reader, complete with videos and interactive exercises. Word count: 1881. Lexile Reading Level: 690L.