The Storm (Part 1)

Exploring the planet, Sheppard and Teyla discover a colossal storm with the ability to crush the city in its current state. The Manarians (first mentioned in "Underground") give shelter to most of the Atlantis Expedition. McKay and Zelenka think of a daring way to power up the shield, but it's no coincidence that the Genii invade the city at their weakest moment.