Solution #1: If the temperature is at freezing or just above freezing, strip-washing hot water on the window and quickly squeegeeing off that water, will be effective. You'll want to replace your water fairly often as the water cools or starts to freeze on glass... That could mean that you refill your bucket with hot water every 8 - 9 windows.
Solution #2: For below freezing temperatures, start with cold water in your bucket and add "Methanol" to your water. Using hot water will evaporate this alcohol faster, so warm or cold water is better is this instance. Methanol is also known as Methyl Alcohol. For our purposes today, we will call it (MA).
MA is easy to find and purchase in it's most convenient form... Auto Windshield Washer Fluid. You can also purchase it in 55 gallon drums if you have a serious need for cold weather window cleaning.
Vary amounts of MA to your water depending on how cold the glass is. The colder the glass, the more windshield washer fluid to water ratio you'll need.
Many windshield washer fluids are already premixed with water and designed to keep fluid from freezing at 20 degrees fahrenheit. Therefore, in some cases, straight windshield washer fluid may be necessary.
Solution #3: You may want to add windshield washer fluid directly to your strip-washer instead of diluting in your water. The biggest reason for this is that the sunny side of the building may not be below freezing. MA can create streaks in the direct sun and it is most effective on the cold side of the building. Adding MA to your strip-washer directly will solve this problem. You can later use the uncontaminated water for the warm side of the building.
Carry a pint or quart sized bottle of MA in your water bucket. Add it directly to your strip-washer as needed.