Leigh Ann Wallace, age 9, of Barstow, California, for her question:
Why is it coldest gust before the dawn?
This topic should be treated as a weather event. After all, it has to do with the air and the temperature outdoors. And these are the main in¬gredients in any weather event. The weather, as we know, tends to have a very changeable mind of its own. So let's not be certain that it gets coldest just before dawn every day of the year.
As a rule, we can expect the air outdoors to become cooler soon after the sun dips down and sinks below the western horizon, but we cannot be ab¬solutely certain that this will happen. We can all recall hot bummer nights when the sultry air seems more stifling than it was during the day. It to happens that nature has very strict rules and regulations and the weathery air outdoors must obey them. Sometimes these rules compel the summery air to stay loot and sultry all through the night. But as a rule, these same rules compel the air to cool off after sunset.
The sun does not give any warmth worth mentioning to the air. The sun¬beams on their way down through the air keep their warmth for the land and seas on the surface of the earth. As the land and water areas gather warmth from the sun, they soon have some to spare. They spread this warmth, or radiate it, upward so it warms the lowest level of the earth's immense at¬mosphere of airy gases. The air outdoors gets its warmth from the land and sea below it. The land and seas get their warmth from the beaming sun. They gather their supply of warmth only when the sun is shining down on them during the daytime.
When the sun sets, this beaming supply of warmth is stopped. As we all know, warm things tend to lose their warmth especially when objects around them are cooler than they are. A bowl of soup soon cools off in a cold room. It has to. The rules say that a warm object absolutely must give away heat to nearby cool objects. After sunset, when the supply of warm sunbeams stops, the ground and the air start losing their heat. A lot of this heat spreads up to higher levels of the atmosphere. As the ground and the air coldest before dawn for Tuesday, December 24, 1968 outdoors lose their heat, naturally they grow cooler. As a rule, they grow cooler and cooler all through the night. So naturally things become coldest at the very end of the night. This, of course, is just before the morning sun pokes its first warming sunbeams up above the eastern horizon.
Clouds tend to act as blankets that stop the heat from escaping from the earth. On hot, sultry nights, the skies are often overcast with heavy clouds or misty curtains of haze. These filmy blankets keep the ground warm and also the air just above the ground. The sultry weather may last all through the night. Maybe a little heat escapes before dawn, but not enough to notice. The air outdoors may be a little, but not much cooler just before dawn.