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When is the first frost date?

Posted by zahzeen 5 Boston area (My Page) on
Fri, Jul 17, 09 at 20:04

I'm trying to plan seeding my fall vegetables and I think should be planting them 6 to 8 weeks before the last frost date. I'm not even sure if the 6 to 8 weeks means when to start seed versus when to transfer new plants. I can sort of figure it out by the dates on the seed pack but really need to know when the "end date" is. I did a Google search and came with a date range of October 5, 2009 (from Victory Seed Company) to November 7, 2009 (Farmers' Almanac). Since those sources differ by 4 weeks, which seems a lot, I was wondering what was the real experience with others in the zone 5 area. I realize ever year is different but would appreciate the "voices of experience". Thank you.


Follow-Up Postings:

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RE: When is the first frost date?

To answer this question, it is important to know more about your exact locality. "Boston area" is too vague. It makes a huge difference if you mean Quincy or Acton for example. Eastern-most Mass in the coastal plain generally inside interstate 495 is zone 6. Areas further north and west than that are zone 5. As far as first frost, the city of Boston does not see a frost, on average, until the first week of November. That date becomes progressively earlier with distance north and west from Boston, and the ocean. Out along 495, the date, on average, is up to 1 month earlier. But elevation differences and the extent to which your area is urbanized makes a big difference, as urban areas hold heat on the clear calm nights that yield frost in fall. The earliest frosts occur in low sheltered valleys in the country-side far from any city or ocean. Areas further west along route 2 in northern Mass (like Orange) can see frost before the end of September in some years.


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RE: When is the first frost date?

Thank you very much for your impressive reply! It's amazing what you learn in these forums. I guess the one month spread does make sense after all. I live about 5 miles to the west of Fenway Park. To be on the safe side, I'll use the third week of October as my end date. Thank you so much again - your reply was extremely informative and helpful.


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RE: When is the first frost date?

You are very welcome. I think the 3rd week of October for your location is probably a good call since the official temperature and frost dates for Boston come from Logan Airport which sticks out into the ocean. And given your proximity to downtown Boston, your location is zone 6 which means the lowest temperature in any given winter stays above -10. Boston (Logan Airport) has not fallen below -10 since January of 1957 (-12). And, in fact, in most winters the city of Boston does not drop below zero, making the city marginally zone 7, without going into the many flaws associated with these zone designations based only on absolute low temperatures.


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RE: When is the first frost date?

Is there a website where one could put in their zipcode or town and obtain the frost date information? Thank you from a new gardener desiring to plant in the fall.


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RE: When is the first frost date?

cpl100 -

I don't know of any resource like that. In reality, anything will still be a guess, since there is variation from year to year as well as over short distances due to microclimates. Any resource will only be able to give you average last frost date unless you live very near someplace like a university or NOAA weather station that keeps detailed long term records.

Even within one zip code, the first and last frost dates can vary quite a bit. My inlaws, who live only about 5 miles away as the crow flies, are probably 500 ft. higher than we are since we are right next to a relatively large river, while they are almost as high in our town as one can get. We get frosts much later in spring since we are in a valley, while they get earlier fall frosts due to their exposed spot and because the water keeps us warmer in fall. There's probably a 3 week difference in spring and 2 weeks in the fall.

Also, this past spring, we had frosts 2 1/2 weeks later than usual - to Memorial Day, so there is variety from year to year.

Your best bet would be to start keeping your own records for the future, and for now, ask around to your neighbors who have gardens.


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RE: When is the first frost date?

There are a lot of web sites with relevant info. Most use data collected by the national climatic data center. The NCDC data (in PDF) for MA is linked below. All the caveats listed by previous posts still applies, but what I like about this list is that it includes different temperature ranges, so you can use it for conservative or optimistic forecasting, depending on your preference at the time.

For other options, see http://www.motherearthnews.com/Organic-Gardening/How-to-Find-Average-Last-Spring-Frost-Date.aspx.

Here is a link that might be useful: ncdc frost dates by town in MA


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