Growing Season? Growing Longer

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**Updates as of 10/30 - Still no 32º reading in Portland or Windsor Locks...so Portland is now just adding on to its record long growing season and latest first freeze ever recorded. The cities of Augusta and Gray, ME have also not managed to reach freezing yet this fall. There's a good shot that Windsor Locks may hit freezing this coming Sunday night. If that happens, it will be only the 2nd time on record that the first freeze hasn't come until November (but it's all-time record of November 5th, 1972 would stay intact).

You probably saw our story on Westminster canceling Halloween plans because of a West Nile threat. As I put in the blog when first written, that's one of the issues later freezes could bring! It's debatable whether or not Westminster really needed to take that action, but I'll leave that decision to you all.

As for Boston and Providence - both may be able to hit 32º or lower on Sunday night. We'll have to see how much cold air this storm can drag on down from Canada. May come up just a tad short in both cities (but definitely <32º for many of the suburbs).

Blog previously posted 10/25/2014:

Garden still green? You're not alone! While we've had a couple of chilly nights in the area (especially the morning of October 20th) Jack Frost hasn't visited every neighborhood. For many towns, especially closer to the coastline, flowers continue to bloom and perhaps you're still plucking a vegetable or two off the vine. This is becoming a trend, and a record-setting one at that in some locations.

Let's start with Portland, ME. Why? Because today (the 25th) is the latest they've ever had to wait for the thermometer to read 32º (with records dating to 1941). In the past 73 years, there's always been at least one freezing night by now. But not this year. The coldest temperature of the season so far has been 35º on that chilly morning of the 20th. So we've got a new record on our hands, and it will continue to grow. There isn't any expected chance for a freezing morning in Portland until *at least* next weekend, if that even pans out. So we're going to end up with the longest wait for a freezing temp by at least a week. It's not just on the fall end, it's on the spring end too. The last freezing temp of the spring in Portland was April 20th, making this growing season 188 days and counting. That's already a record, the previous being 184 in 1990!

Maybe more interestingly, the wait has been long many times in recent years. Of the top eleven latest 'first freeze' dates, six of them have come since 2005. With this year, it will make 7/12. On top of those figures, the previous record for latest freeze was just set last year in 2013. That's a pretty significant cluster pointing toward warming times in New England.

Statistics are from the Northeast Regional Climate Center

How about Windsor Locks, CT? A location farther away from the moderating impact of the ocean. It's also not an urban center (although there is a little bit of sprawl around the airport). They too are waiting for their first freeze of the season. There's still a bit of a ways to go to reach their record - which is November 5th of 1972. With the current forecast, the #2 spot on record is a lock - it's just a question of whether or not it happens next weekend. There's also a recent cluster here, with this year making it six out of the top 10 years for 'latest freeze on record' coming since 2005.

There's still a much longer time to go before the jury comes back with a verdict on Boston and Providence. They're larger urban centers (with heat island effects) and are both on the water which can help moderate overnight temperatures. Boston's latest first freeze is alllll the way into December. To be exact, it's December 6th of 2009. The growing season was an insane 254 days that year! Our growing season in 2014 is just 190 days long so far. That will be a tough record to reach. For Providence the latest on record is November 19th of 1935...also quite a bit of a wait left.

The most recent National Climate Assessment produced some statistics on the lengthening growing season both across the country and right here at home. According to Climate Central "These calculations are based on the 1991-2012 time frame relative to 1901-1960. (NOAA calls it the "frost-free season," but temperatures below 32°F count even if frost doesn't actually form)." It is essentially what you'd expect to see in a world that is gradually warming up.

If this trend continues, there's more of an impact than just being able to pick tomatoes in late October. It can change the types of vegetation that grow in different parts of the country. For example, remember back to 2012 when the USDA changed the growing zones due to warming trends. When the new map was released, the agency explained that "The new map is generally one 5-degree Fahrenheit half-zone warmer than the previous map throughout much of the United States. This is mostly a result of using temperature data from a longer and more recent time period; the new map uses data measured at weather stations during the 30-year period 1976-2005."

Later freezes also mean waiting longer for the mosquitoes to be killed off, increasing the length of time that mosquito borne illnesses like EEE and West Nile Virus are a threat. For allergy sufferers, it could also mean a longer season to deal with allergens like ragweed. Can't tell you how many emails we've received when a good freeze will rid us of it this year!

So how about a forecast? When will we finally all awake to icy windshields and a frosted wonderland on the grass outside in 2014? Well right now we're monitoring a possibly strong cold shot that would spread down into the Northeast next weekend (November 1st and 2nd). While the signal is there in the models, it's definitely not a lock. Normally we'd like to see something like a big typhoon out in the Pacific helping to build a strong ridge and subsequently send a trough and cold air tumbling down into the eastern U.S. At the moment, we don't have that. But there's been enough of a trend to say it's at least a respectable shot that we'll get the coldest temperatures of the season flowing on down Halloween night.

GFS ensemble mean forecast temperature anomalies for the period Oct 30th through Nov 4th. Source: Weatherbell

The GFS ensemble mean shows a significant cold signal for the eastern U.S. in this time frame, which is a good sign for cold lovers. I've also included some ECMWF EPS probabilities for minimum temps below 32ºF next Sunday morning. Right now, it's showing about a 30% chance of it happening in Boston and Providence, and a 40-50% chance of it happening in Windsor Locks and Portland. So there's definitely potential here. If we don't get it next weekend, who knows how long into the fall it will take for these cities to freeze up?

ECMWF EPS (European Centre for Medium-Range Weather Forecasts Ensemble Prediction System) probabilities of temperatures at or below 32º during Saturday night/Sunday morning next weekend. Source: Weatherbell