IStock Photo 5012629 © Peter van den Berg

Ah, Christmas. The shopping stampedes, the questionable eggnog, the…risk that your tree will catch fire and burn down your house?

Christmas tree fires are rare, considering how many people in the US drag a shedding evergreen into the den each year. The odds an American household celebrates Christmas are 1 in 1.06 (94%), and the odds are 1 in 1.14 (88%) that one of those households usually puts up a Christmas tree during the holiday season. The US Fire Administration estimates that natural trees get hoisted up in more than 33 million homes each year.

The odds a house, apartment building, or other residential structure will have a fire in a year are 1 in 309.7. The odds your tree will start one are 1 in 430,100. That’s about 250 fires a year. It’s far more likely you'll injure yourself in a fall related to your holiday decorations, perhaps while arranging rooftop deer or tripping over the tree skirt; the US Centers for Disease Control and Prevention estimates the likelihood of gravity-related holiday embarrassment—or tragedy—at one in 12,346.

Even in peak season from November through January, the numbers are low. Christmas tree combustion contributes to about 25 of the 2,000 injuries blamed on house fires during the holidays, 6-14 of the 500 deaths, and $6-14 million of the $500 million in property damage.

However, Christmas tree fires tend to be deadlier than other house fires. While about one person died for every 134 house fires from 2003-2007, the numbers were one in 18 for Christmas tree fires.

That may be because about half of these blazes spread beyond the room with the tree. Smoke and flames that lick into bedrooms, kitchens, or other areas of the house cause 94% of Christmas tree fire-related deaths. And it happens fast. The Building and Fire Research Laboratory at the National Institute of Standards and Technology has a terrifying video on its website showing how an entire room can go up in flames within seconds of a tree igniting. This isn’t the kind of open fire you want for roasting chestnuts.

The National Christmas Tree Association protests that Christmas trees do not start fires. True, it is electrical shorts in decorative lights, heat sources left too close, and open flames from candles or matches that set trees aflame. In fact, candle-triggered house fires of all kinds jump 400% during the holiday season. Celebrating Christmas isn’t a prerequisite, either; unattended menorahs, too, have been known to burn down houses.

The critical determinant between a spark and a four-alarm blaze is lack of moisture. Dry trees are much more likely to catch fire. It might not be the exemplar of Yuletide décor, but keeping a freshly cut tree in a bucket of water spreads moisture all the way to the tips of the tree's needles, making it much harder to ignite. “Well-watered trees are not a problem. Dry and neglected trees can be,” says the US Fire Administration. The NIST website features a telling side-by-side comparison, wherein the “wet” tree fire fizzles before it even gets started. This may explain why more than a third of Christmas tree fires happen between Christmas Eve—when the lights go on and unwatered trees have likely dried out—and January 2, when many people take their trees down.

Topping off a pail every day seems like a small price to pay to help prevent these rare but serious fires. With winter weather and visiting in-laws, the holiday season is treacherous enough.