 Why are Bal and Ethaniel so cold?
"It's not what they've done," said Bal, the second alien. "I may remind you that in two months twenty-nine days we're due in Willafours," said Bal. A meteor shower could pass over and their clumsy instruments could interpret it as an all-out enemy attack." "What's worse is that I now find they also have missiles, range one thousand miles and upward. We can't help them," said Ethaniel. The southern plains were green, coursed with rivers; the oceans were blue; and much of the northern hemisphere was glistening white. Ragged clouds covered the pole, and a dirty pall spread over the mid-regions of the north. It's their winter."
 Bal and Ethaniel are cold because it is winter where they have landed on Earth.
 People are mistaking them for the types of angles seen in Renaissance paintings. It is likely they are wearing little or no clothing.  They are cold because the clothing synthesizer on their spaceship was not equipped with the materials needed to make cold-weather gear.  They are cold because the planet they come from has a much warmer climate, and they were not prepared for cold weather.  Bal and Ethaniel are cold because it is winter where they have landed on Earth.