First frosts vs. first flakes: Is there much of a correlation?

*A FIRE WEATHER WARNING IS IN EFFECT. Click here for more details**

In honor of the chilly mornings we’ve been experiencing the past few days, I decided to conduct a study that would ultimately prove to be not nearly as exciting as I hoped for, but it’s an interesting study nonetheless. Have you ever wondered when our average first frost is? No? Well…darn. I thought you might. Well, then have you ever wondered when our average first snow is? No?! Really?! Wow…then I DEFINITELY need to share my findings!

Amidst busy college projects and reports, I’ve set aside time to check the past 10 years of weather records (2001-2011) to see when the Bremerton area received 1) their first frost and 2)their first flakes. The criteria for frost is freezing or below and the criteria for flakes is they must be flying in the air, not necessarily sticking. So here’s what I found:

  • 2011 Frost: October 16th; Flakes: November 18th
  • 2010 Frost: October 14th; Flakes: November 21st
  • 2009 Frost: September 30th; Flakes: December 14th
  • 2008 Frost: October 10th; Flakes: December 13th
  • 2007 Frost: October 27th; Flakes: November 1st
  • 2006 Frost: October 30th; Flakes: November 26th
  • 2005 Frost: October 27th; Flakes: December 1st
  • 2004 Frost: October 24th; Flakes: January 6th (ouch!)
  • 2003 Frost: October 29th; Flakes: November 20th
  • 2002 Frost: October 13th; Flakes: December 28th (ouch again!)
  • 2001 Frost: October 28th; Flakes: November 28th

You wouldn’t believe how much I’ve looked over these numbers trying to find some sort of correlation. Does a later frost lead to a later snow? Not necessarily. In fact, one of our latest frosts in 2007 brought us our earliest snow in the past 10 years on November 1st. So does that mean a late frost means an early snow?!?! Hold your horses. Remember October 24th, 2004? Our first flakes weren’t spotted until…gulp…January 6th, 2005! Makes me nauseous to even think about it…

Ah! What about the time span in between the first frost and first snowflakes! Surely that will tell us something! Well, not really. In fact, 5 years are two months apart, 5 years are 1 month apart and one year is a week apart (2007). Drat! Looks pretty 50/50 to me.

Let’s analyze the colors for a moment. Blue indicates La Nina years while Red indicates El Nino years. This beautifully illustrates what these weather patterns do to our winter climate. Since 2007, La Nina has made more frequent appearances, and in all these years the frost came right on time (mid October) and the flakes followed shortly after. Conversely, look at the El Nino years. Aside from 2006’s anomaly, the flakes seemed to come consistently later. Yes, this is an El Nino year, but not a strong one, so we could go either way.

But a closer look could reveal something maybe only moderately intriguing. Then again, I get entertained easily. From 2001-2007, on average the first frost occurred at the end of October. Notice how from 2006 we get an earlier frost every year until 2009 where we peak at the earliest frost on record in the past 10 years: 2009. Then watch what happens after we hit 2009. 2010 we drop to Oct 14th, then on 2011 we drop to October 16th. Do these numbers look a little bit like a wave to you?

The first snows in each of these years, however, never seemed to come any earlier. In fact, these records show that pinpointing a first snow is still very much a gamble in this area, however if one insisted on betting I think sometime in November during an non-El Nino year would be a good shot. So that begs the question: when are we going to get our first frost?

According to the data I’ve received (which seems almost more like a mix of random numbers than a trend) I would go out on a limb and predict we’ll see our first *recorded frost in the Kitsap area in mid October, say sometime a little after the 16th.

Let me know if you see any other interesting trends in the numbers. Believe me, I tried hard! 🙂

Enjoy the rest of your week, everyone! We are well on our way to possibly reaching the 80s yet again on tomorrow.

Matthew Leach

Forecasting Kitsap