Possible Clues:

• It affects the weather in a winter battle zone
• Leading edge of cooler temperatures
• It ushers in lower temperatures ... and what the answers to starred clues can have
• Weather map line
• Weather (forecast) feature
• Harbinger of lower temperatures
• A century old, and not back for the weather
• Dispassionate manner sometimes a feature of weather forecast
• One does not get back to make it not so hot
• It can make one wear heavier clothing