Mild weather right through the winter? Temperature barely straying below the freezing mark at all? Well, it's not all good news. In places which always have a cold winter with good snow cover, a mild winter can be downright disruptive to growing cycles.
Grass keeps on growing right into December. Apple blossoms start blooming in February. Tulips sprout in January!
And that's all well and good, except that in a four-season climate, a mild winter usually doesn't mean no winter at all. When the late frost hits (and there's always a late frost), it kills everything that's sprouted.
When apple blossoms sprout unseasonably and are killed off, it means no apples that year. That kind of thing's disruptive and price-raising.
When it's just local apples, it's not so bad. After all, other places grow apples as well, and some of their winters and springs are perfectly normal. As long as someone's growing apples, all that's going to happen is that the price of apples is going to rise. Of course, that could still mean that you can no longer afford to make your world-famous apple pie for Thanksgiving.
But mild winters also strike at staple crops. When there's not enough snow cover, winter wheat can't survive the winter. The seed's forced to the surface by freeze-thaw cycles, where it's destroyed completely.
On top of that, the bare topsoil in places which grow winter wheat is exposed to winter winds. Normally, the snow is supposed to hold it in place. If there's no snow, there's nothing to stop the wind from stripping the topsoil. That kind of damage takes centuries to fix naturally. In the meantime, farmers have to dump extra fertilizer on their soil to keep their crops growing.
However, there's also places with unique products which absolutely depend on a deep freeze. Those crops aren't available anywhere else in the world. You can't harvest maple syrup if the temperature hasn't gone down below freezing. You can't have ice wine if the grapes haven't frozen solid on the wine. In the winter of 2011-12, the Niagara region's in danger of losing its ice wine season completely!
Spread of damaging species
Harsh winters usually limit the spread of ash borers, pine beetles, and other damaging insect species. Mild winters give them a free pass. Next spring is going to be bad.
Sleeping seeds don't take up any water to speak of. In the spring, seeds sprout and other plants are ready to wake up. That's perfect timing to take advantage of the water released when the winter snow cover melts in spring. This is what replenishes soil, wetlands, and ground water every year.
Without good snow cover, very little water reaches the soil and aquafers. If it's also cold enough for soil to freeze, any rain that fell over the winter can't even make it into the soil. It just runs right off! Between that and the lack of snowmelt, spring's already starting on a drought footing. Let's hope there's enough extra spring rain to make up the difference.
More damage to fix
In four-season climates, it's not the snow and cold that causes most winter damage. (Well, aside from frozen pipes, and those are avoidable.) It's the freeze-thaw cycle at either end of winter. In a mild winter, that freeze-thaw cycle just keeps on repeating day after night after day. That means the damage caused by temperature changes during a mild winter can be a lot worse than damage during a normal winter.
More ice and ice storms
When it's well above freezing, precipitation falls as rain, and roads eventually dry off. When it's solidly below freezing, precipitation falls as snow, and roads can be cleared by snowplows.
When it's hovering right around freezing, precipitation sometimes falls as rain and freezes onto the colder roads. Other times, it falls directly as ice. Either one makes for just about the worst possible conditions for driving. A bad ice storm followed by low temperatures can damage snow plows.
It's even worse for electricity grids. The worst that snow can do is to bring down a few branches onto live wires and cut the electricity that way. Some lines may bow down because of the weight of the snow, and a few may short out. That can be bad enough, but it's no match for what ice can do. That's because for the most part, snow can't stack up on electricity wires and towers the way ice can. Ice clings and builds up, and it's much heavier than snow.
In a really bad ice storm, like the one in Montreal in 1998, the weight of the ice can twist and topple electricity pylons, completely taking down the grid. Montreal electricity standards are built to take up to an inch and a half of ice, but nobody could deal with four straight days of ice. Montreal usually gets more snow than just about any other place in Canada. The Montrealaise (residents of Montreal) prefer dealing with that normal level of snow over ice any day!
Wait, MORE snow than usual? It's not true everywhere, but it's all too true in most of the snow belt off the Great Lakes. In normal winters, the Great Lakes snow machine turns off when the Lakes freeze over. However, mild winters mean that the Great Lakes don't freeze over at all.
If the Lakes don't freeze over, there's nothing to stop the bitter winds off the prairies from picking up lots and lots of moisture. All of that moisture turns into snow squalls downwind of the Lakes over the snow belt. In every part of the snowbelt that's not directly downwind of Lake Superior (which never freezes completely), those kinds of squalls usually stop around early February.
That's why, in a so-called mild winter, the snowbelt regions of the Great Lakes often have record snowfalls. Each time the wind picks up and comes from the right direction, the snow will start falling all over again.
To make matters even more fun, all of the snow from a system of snow squalls may melt completely in a week. In the meantime, you still have to get rid of it!