Autumn is here. But when does Bad Fall arrive?

PHOTO: When November comes, the sun abandons the Fraser Valley bringing rain—a lot of rain. 📷 Harry Beugelink/Adam Melnyk/Shutterstock

The weather has turned. The days are shorter and cooler, and it has actually rained.

Fall, both in spirit and on the calendar, is here.

But autumn is a weird season in the Fraser Valley. It can be beautiful and perfect. It can also be utterly miserable and disaster-inducing.

So how much more time do we have to enjoy the outdoors?

We consulted the data at Weatherspark.com to answer the Fraser Valley’s biggest weather conundrum: When does Good Fall end and Bad Fall begin?

For the purpose of this exercise, we’re using the Weatherspark data for Abbotsford, which sits in the centre of the Fraser Valley. Because of the moderating influence of the ocean, temperatures tend to fall a little earlier to the east and a little later to the west. You also may get more rain depending on your proximity to moisture-trapping mountains.

The transition from the sunny, hot days of August to the rainy doldrums of late-November is a relatively steady progression. But we’re going to try to pick a day when the average day goes from good to not-good.

To start, though, we need to know when the worst day of fall is. Weatherspark is pretty clear on that front: It’s Nov. 18.

Nov. 18 has both the greatest daily chance of rainfall—61% in Abbotsford—and the most monthly rainfall for the month-long period before and after it. By mid-November, the average high temperature is less than 10 C. This also checks out anecdotally: Nov. 18 is just a couple days after when the atmospheric river hit in 2021. (The data itself comes from models based on weather reports from between 1980 and 2016.)

But it’s a slow descent before the weather gets that bad.

We’ll break the weather into a few component categories to figure out when the weather goes from decent to ugh.

Heat

Good Fall ends: Oct. 20ish

After a baking August, September’s temperatures are downright comfortable. Even on Oct. 1, the average high is still nearly 20 C—and, as last year showed, can obviously exceed that by quite a bit when the sun starts beating down. By Halloween, though, the temperatures are more winter-y, with average highs of just 12 C and lows of 6 C.

You can probably put the tipping point just after the middle of the month, when most days are cooler than 15 C and evenings and nights can be frigid.

Sky

Good Fall ends: Oct. 20

It’s not the case everywhere, but in the Fraser Valley, winter also brings much cloudier skies.

In early August, according to WeatherSpark, 71% of the sky is clear of clouds on an average day. By Nov. 30, only one-quarter of the sky is cloud-free.

One tipping point comes just before the end of September, when the average day goes from mostly clear to mostly cloudy. (Cloud cover data comes from NASA data, Weatherspark says.)

The sky grows increasingly cloudy throughout October until Halloween, when only 30% of the sky is visible on average. It gets a little cloudier and darker from there, but not by all that much. By the start of November, the Fraser Valley has definitely entered the cloudiest days of winter.

Those overcast days, when no blue sky is visible, also become increasingly common. On Oct. 20, there’s about a 50/50 chance that the sky will be completely obscured by clouds.

Sun

Good Fall ends: Nov. 5 at 2am

The sun is, obviously, also making shorter appearances even when it is visible.

At the start of fall—Sept. 22—days are still longer than nights. Though not by much (the days are 12 hours and 12 minutes long).

The sun begins to set less than 12 hours after it rises on Sept. 25. (Your sun-mileage will vary depending on proximity to mountains.)

Still, October can seem tremendously bright compared to November. And for many, no day is bleaker than Nov. 5. On Nov. 4, the sun sets at 5:43pm. On Nov. 5, it’s gone at 4:41pm, before many people get off work. The culprit, of course, is the end of Daylight Saving Time.

Wind

Good Fall ends: Oct. 15ish

The wind becomes increasingly blustery throughout the fall. In particular, the windiest days get substantially windier, peaking in December. The midpoint here is right around the middle of October.

Rain

Good Fall ends: Oct. 24

More than anything, fall is when the Fraser Valley’s climate goes from very dry to legendarily wet. And while rain becomes more and more likely through August and September, October is really when the rain hits in full.

At the start of the month, rain falls on just one-third of the days. By the end of the month, more than half the days require umbrellas. Things get even rainier in November, peaking at the middle of the month. But by the time Halloween rolls around, we’re already firmly into rainy season. If you’re looking for a specific day, WeatherSpark says there is a 50/50 chance of rain on Oct. 24. After that, bet on rain. Before that, bet against it.

Readers

Recently, we asked Current Insider members when they thought Good Fall ended and Bad Autumn began. We gave them five choices, plus the option to tell us another date.

Of the 326 votes, the most commonly chosen date was Nov. 10. But only one-third selected that option. About a quarter of respondents selected Oct. 31. And another 30% of you chose an earlier date.

So we are going to try a second poll, with more date options.

Postscript: What about winter?

There is one lingering question (at least among certain FVC colleagues of the writer): what separates Bad Fall from winter?

By late October, it’s increasingly cold and rainy. Is winter really much different?

The data suggests that it’s not—usually. But what separates our Bad Fall from the winter that roughly runs from mid-December to February is the threat of snow.

Temperatures are roughly five degrees cooler at the end of November than the start. And that makes a world of difference when it comes to snow—and especially the chance that snow, if it falls, will stick around and make everything very wintery.

Snow is relatively rare in the Fraser Valley. And it rarely falls in November—over the last decade, the most snow that has fallen over the entirety of the month was the 11cm recorded last year.

December, on the other hand, brings the threat of large and long-lasting snowfalls that dramatically change the appearance and pace of life in the Fraser Valley. So no, Bad Fall is not winter.