The average cost to have a professional install Christmas lights on a roof is about $420, with most homeowners spending between $220 and $650. Some companies may charge between $1.25 and $3 per square foot, excluding the cost of the lights. For extensive or complex jobs, the cost can exceed $1,000. While doing it yourself can save money, it is only recommended if you are comfortable working at heights.

Professional holiday decorating services cost between $300 and $2,500 or more, with an average cost of about $1,500. The total price depends on the size of your home, the extent of the work, your location, and whether materials are included. Simple interior decoration may cost around $300, while a combination of interior and exterior work often totals around $800. For large or extensive design services, you could pay $2,500 or more. Common service costs can include: exterior holiday light installation ($400), Christmas tree decoration ($200–$600), interior holiday design ($50–$200 per hour), and holiday landscaping ($50–$100 per hour). Note that some prices may only include labor, not the cost of the decorations themselves.

Cold weather can cause older incandescent Christmas lights to fail by causing cracks in the finish or the glass itself. Modern LED lights are affected in the opposite way and perform even better as the temperature drops. 

Heavy amounts of snow could be a problem. In many climates, lots of snow on your rooftop can lead to freeze-thaw cycle that create ice dams, which can damage rooftops. But if you’re using shingle clips, this snow poses an additional problem: As it melts and freezes, it can easily dislodge clips you’ve placed on your roof.

You can clean snow off your roof after a fresh snowfall while it’s still lightweight, but brushing off snow can also dislodge your clips. If you get a lot of snow, then roof clips become less viable.