Very interesting map! Ive seen it a few times before. I really like the zoom feature, but I dont like how it doesnt factor the heat island effect of major cities at all. Manhattan Island is almost always warmer than surrounding areas on cold nights and is actually only a zone 6b on this map whereas areas of Long Island (only a few miles away from the city) is a zone 7. Im in a zone 6b according to this map even though the area hasnt seen a sub zero winter since, I think, the early 80s (and even then some places in the area saw temperatures not much below 0F).
Its a great map though if you want to know for sure which plants wont die even in an extremely cold winter.

Thanks for sharing!
-Alex

Tropicalzone, at the same site, there are also maps available that are based on greater and more recent data.--Don't ask me how to get to get there as I got to them once then had to rely on my 'history' feature to get back to them. On the older maps, I am 6b as well, but on the new maps I pop up to 7a--as you should too. The older maps seem MUCH broader, the new ones, seem to make much finer distinctions as the zones seem to snake around running N/S as well as E/W. Newer ones seem more accurately to capture microclimate variations--especially those that arise from urban and dense suburban heat islands. If that weren't confusing enough, I live in 7a (albeit not on all maps), and just a stones through from Manhattan but the Weather Channel on my cable TV (for God knows what reason), gives me all local weather data for a city 50 miles (one hour) west of here and at least 1 gardening zone away (if not more!). Therefor, I usually automatically tack on several degrees to the minimums. (For maximum temperatures, I either add or subtract depending on the time of the year.)

These maps can be useful tools but I also feel they can be given excessive importance. Lots of factors are involved in considering cold hardiness (duration, snow cover, wind exposure, soil moisture, etc.) Still, it could be worse. We live in the East--ever take a look of what happens to gardening zones in the WEST. The lines curl every which way and things get really complex!

Thanks Nj. Im going to keep on looking for that newer USDA map on that website. I did find first and last frost dates. The First frost date map was pretty good and I am right inbetween Nov 1-10 and Nov 10-20 so I guess my average first frost is usually around Nov 5 -15 (it was much later this season and last fall too thankfuly!) The last frost map for NY seemed a little off since the scale on the side only went down to May 1th even though their were colors that were for much earlier dates. Last frost is usually early April and you arent really safe from frost until late april. By early may most of the plants are outside according to the weather.

-Alex

Okay, here's the page to which I was referring. This one's for NJ, but you should be able to use it to link to NY.

Here is a link that might be useful: Interactive NJ gardening zone maps/revised

Thanks for the link. Im a zone 7a now and pretty close to a zone 7b! I really find it interesting how they have a zone 6a right along the New Jersey Coast, but after looking at the record lows for that area, I agree that its a zone 6b there. Im surprised that they dont have New York City as a zone 7b, but most of the weather data for Manhattan comes from Central park which is cooler than some locations in the denser parts of the city and the city also has lots of warm and cold microclimates so a zone 7a is probably best.

Thanks again! I like this map more than the current USDA zone map.
-Alex

Hi Alex,

Some older maps place NYC as a zone 6b and its been changed to 7a. Even some older maps have Brooklyn as a 7a. Fact is, last year we were 8a and it fluxuates year to year. Usually most of the city is 7b, and the Bronx dips to 6b a lot. Plus you should consider Manhattan has not hit the freezing mark yet and your area has. Heat Islands are ignored by the overall zone maps.

Once in 8-12 years we do have a 6b winter. Hope this is not the winter my friend :) We are both over do?

Its the duration of our cold that kills off palms more in our area.

Yeah, we are overdue for a cold winter! 2004 was the last cold winter and it had a low temperature of 2F. There have been colder, but you have to go back probably 15 years or so to get low single digits/around 0F.

Did you get a frost yet? I was in Manhattan this past weekend and I saw croton that was still THRIVING as well as many flowering annuals and somewhat tender palms. However, that was before we even had a frost here so Im not sure if those plans will still be thriving now. Either way it looks like the entire NYC area will definitely have a killing freeze very very soon (the forecast looks very cold!!)

As far as USDA zones they really are only a guide at best. I think NYC best as a zone 7a. Many winters are above 5F and the average lowest temperature each winter does qualify NYC to be a zone 7b (I think the average LOWEST temperature for NYC for the past 15 years or so is 7 or 8F with JFK around 9F). Still every once in a while you get winters below 5F and even around 0F. Then you have those rare winters that do go below zero and even though it isnt common, it still does happen. Ive seen zone 8a plants come through our winters just fine (according to the plant), but eventually they will be severely damaged, or dead. Zone 7a plants (like many camellias) will be fine even in our coldest winters and I have seen camellias in the area that have survived for over 50 years without being severely damaged.
The duration of Cold, lack of sunlight, and high amounts of moisture are all problems our area faces every winter!

Good luck!
-Alex

Hi Alex,

I have made similar observations. I have some interesting news for you about our first freeze. Last night Central Park went to 34* last I heard. In my court yard the water in the bird bath iced over slightly but as usual water dishes within 10 feet of the building were still liquid. All the brick creates a mini-heat island. Temps rebounded fast to the upper 30s this morning. I think there are many overlooked nooks of Manhattan that really do not freeze that much with heated basements and subways facing south. The trick is to find a piece of ground and plant a cold tolerant palm or camiela there.

I agree and would zone Manhattan and the other parts of the city 7a-7b considering its very rare and short lived for us to drop below 5*. The Bronx is an exception, just being a little more north and having some tad elevations I'd zone them 6b - 7a. They actually recieve more snow than Brooklyn regularly. When I visit the Bronx in winter I notice they have snow on the ground more often when anything below Central Park North was just rain or sleet. There's an invisible line that sets up in some snow storms.

The bronx is definitely cooler than most parts of the city. The areas along the water arent too bad, (probably a zone 7a) but the northwestern most sections definitely are exposed to much more cold (and are probably about a zone 6b, maybe a little bit cooler). There are definitely spots in Manhattan that do not freeze, or at least dont freeze often. Some places are very sheltered from wind and have warmth from the buildings or ground and cold probably keep lots of subtropical plants very happy. Brick seems to be really good with frost protection as well. I have some lucky bamboo outside and Tradescantia zebrina that are completely untouched because they are near a brick wall or the house. Im trying some cast iron plants right against the foundation of the house as well ,and Im really looking forward to seeing how much, if any, protection the warmth from the house will give them! Im just going to cover them from moisture.
The rain snow line usually does cut through the bronx during a lot of storms. I dont remember any major snow storms in the city that was ALL snow, but the bronx might be an exception.

Good luck!
-Alex

Neat map! it seems to tend COOLER for my area, and many areas in the mid Atlantic, but still neat. I also love the tree / plant distribution maps as well. Thanks for the share! have it bookmarked now.

Here's the supposedly revised/updated map for Virginia and vicinity.

Here is a link that might be useful: Revised Virgina Map

Alexandria VA looks pretty mild on that new map! They have it down as a zone 8a and a zone 8b right along the river! I can see it as a borderline zone 8a and even a solid 8a, but I think the 8b is a little too warm (just like the 7b might be a little too big for my area). Winters can get cold and definitely below 15F somewhat often (Im not really familiar with the climate though so more info is appreciated!). I think Virginia Beach is probably a zone 8b and Norfolk too. They are further south and closer to the water. I do still think that the revised map is pretty good!

Good luck!
-Alex

A little better revision. I only see a 7b for Alexandria though. I would put it at a cool 8a. That said, it can get down to a 7a winter some years here, and some years it can be close to an 8b winter as well. This year (at least the least few weeks) are looking right at a solid 7b. Definitely better than it was. I'm pretty sure that Va Beach / Norfolk area is much more an 8b than anything as well. Does anyone know who did this map? Just wondering.

That's a better VA map - more current.

I think the formula they use is the lowest temp every 10 years determines your zone. I think it should be every 5-7 years because we can go a entire decade with 7b winters in NYC.

Wow, pretty accurate for me here in cali. First and last frost dates were dead on this year too. Thanks!