When does spring hit the Fraser Valley? We looked at the numbers.

Spring is coming. Eventually.

Winter technically ends on March 20, but most people have their own concept of just when spring gets here. (If you’re a groundhog in Ottawa, you probably have a different answer than a journalist in Chilliwack.)

So, with this winter dragging, we have turned to the weather data website Weather Spark to get a better read on when we can celebrate the arrival of a new season. Unless otherwise noted, the dates here reference the Weather Spark estimates for Abbotsford, though all figures and trends are almost identical across the Fraser Valley. (Chilliwack/Agassiz is a tiny bit wetter and cloudier than Abbotsford.) The Weather Spark data itself comes from NASA.

Theory 1: Winter is over when there is no chance it will snow

If you subscribe to the theory that snow equals winter, then you could almost argue that the Lower Mainland rarely descends into winter. Still, there are several months when we are faced with at least the possibility of snow. The highest daily chance of snow runs from approximately December 17 to Jan. 10. After mid-January, the odds of snow get narrower and narrower. Snow is quite rare, though still possible, all through February. But Weather Spark’s modelling suggests that by March 18, there is effectively no chance of snow, heralding the return of spring.

Winter over: March 18

Theory 2: Winter is over when the clouds start to lift

This theory gets you the longest winter, unless you split the data very finely. The chances of seeing the sun is lowest in December and January. The odds rise a tiny amount in the first half of February, but remain depressingly low until April begins. Only then does the sun begin showing its face more reliably. Best chances of sun: Aug. 3 (71%). Worst chances: Nov. 30 (25%).

Winter over: April 1

Theory 3: Winter is over when it stops raining so much.

If you equate cold drizzle with winter, then March 24 is the day things start to get better. Until that shift, any one day brings an almost 50/50 chance of rain in Abbotsford. But that disturbingly high probability of precipitation begins to decline in late March. The chance of rain continues to decrease all through April. By April 30, the odds of a rainy day is 33%.

Winter over: March 24

Theory 4: It’s all about the temperature

This theory makes natural sense, but doesn’t do much for separating one season from another. Temperatures bottom out right around the turn of the year, then increase consistently throughout the first seven months. There is no obvious point at which the temperature begins to rise at a quicker rate. So, let’s just look at the point at which the high temperature exceeds two arbitrary points: 10 C and 15 C. The average high temperature crosses that 10 C mark on Feb. 28. It hits the 15 C average around April 16.

Winter over: Feb. 28 (or April 16)

Theory 5: Spring is here when days are longer than nights

The first day of official spring corresponds closely, but not exactly, to when the sunrise-to-sunset period begins to be longer than 12 hours. This year, the tipping point is March 17, when the day will be 13 seconds shorter than an even 12 hours. March 18 will be 3 minutes longer.

Winter over: March 18

Theory 6: The lilac leaves will tell you when spring is here

Flowers bloom at all different times, and so do trees. But few say spring quite like a lilac. The USA National Phenology Network (USA-NPN) collects data to create its own ‘spring indices’ based on when lilacs and honeysuckels get their first leaves across the United States. And fortunately, the Fraser Valley borders the US, so we can use the data to get a local date. According to the USA-NPN, lilacs in Sumas, Wash., get their leaves around March 1, give or take a day or two. You can explore the map here.

Winter over: March 1

Theory 7: The weather often feels notably better as February goes on. Might spring normally start then? Here's one argument (that probably doesn't pass muster this year)

If the first half of February sometimes seems like things are changing, you might be onto something. While there is no sudden shift, February is the first point where a range of measures all get slightly better around the same time. Over the first two weeks of February, overcast days become moderately less frequent (60% of days to about 55% of days). Rainy days become a tiny bit more rare. And the amount of rain falling on those days decreases moderately (by about 10%). Snow is increasingly rare, and when it does appear, there’s less of it and it melts quicker. Throughout this period the temperature rises consistently, and by mid-February roughly a quarter of our days have a temperature above 12 C. All those factors combine to make the weather better, and less winter-y.

Winter over: February