MAJOR SHOCK / The difference a few years can make / NOWData Update to US Atlantic Coast PHZM

[nyy_ct]

Don’t shoot the messenger, some major surprises in the data but at the same time a continuation of the trend seen in the 2023 Map put out by the USDA for 1991-2020. 
 

This map is “quick and dirty” using Google earth and may trigger some climate change skeptics. It covers 1995-2024 using NowData. 

Shockingly, the Virginia Beach-Norfolk is thoroughly 8B, 8A has engulfed the entire Chesapeake, Lewes, DE popped up to a low 8B, 8A has crept up the NJ shore, parts of Long Island (La Guardia in Queens, NYC to Syosset) are now 8A, Montauk, NY on the tip of Long Island is now 8A, several stations in coastal Connecticut are now 7B (crape myrtles going “viral” now in parts) parts of the Outer Banks, NC are now 9B (Okracoke), as is Charleston, SC. Richmond and suburbs and Williamsburg in Virginia are now 8A, as is the urban core of Charlottesville, Virginia. The biggest jumps are happening in coastal areas in the middle 60% of the US eastern seaboard. Also, the Western Florida Keys are now showing 12A.

The US east coast now ranges from 5B in Down East Maine to 12A in Key West, and it appears zone 8B has become modal for many areas in the coastal region.

Strange finding 7A fairly far south in Central Virginia when it is rapidly expanding north closer to the coast.

The same finding 8B in northern Peninsular Florida when Lewes, Delaware is showing a (barely) 8B designation now. 7B appears rapidly expanding in the upper mid Atlantic/northeast and 8A in the lower mid Atlantic. If the patterns hold, where will we be in 2030? 2049?
 

Obviously, zone alone does not factor in duration of subfreezing whether, it’s only a mean (expected value) derived from a trailing set of years, nor does it indicate the variance or distribution or probability of warmer or lower cold extremes relative to that mean. There was no interpolation or smoothing of data here. I understand the limitations in usefulness and implications of data quality/availability in certain locations, and, obviously, that 2024 has not finished, but still fascinating to see in my view.

There was no data interpolation to build the map, and as I said just “quick and dirty” but I skipped over stations with clearly less than 7 or so years of data to work with.

Enjoy (or cringe). Thanks for having a look ladies and gents.

 

 

 

[PalmsInBaltimore]

yes, definitely a continuation of the trend.

As for the uneven spread, I don't find it strange at all that the zones are rising along the East Coast faster than they are further inland. I'm looking at the 2023 USDA hardiness zones, and you can see basically the transition from the coastal plains in Delmarva, the Carolinas, and Georgia, rising to piedmont and then to the appalachians, alleghenies, blue ridge, etc. The 7a "fairly far south" in central virginia is near charlottesville and skyline drive in the shenandoah valley. almost alpine in terms of the different microclimates and shadows created by the ridge and valley geography.

As for the Florida panhandle, that is where the highest elevation in the state (a mere 100 meters/345 feet) is, so I'd chalk that one up to elevation affecting the hardiness zone.

Here in Baltimore, it is pretty unexpected how much of the city's metro area is now 8a. The fall line appears to come into play. Areas below the fall line are 8a; areas above it are 7b, and then dropping to 7a the higher up you go, and down into zone 6 in western maryland. 

Obviously areas near water are warmer. There aren't many trees in the Delmarva peninsula, and it's pretty flat. I wonder if that's why it's mostly 7b, despite being a low-lying area surrounded on three sides by water, whereas the waterfront edges of it are 8a.

[Jimbean]

That map is trash

[Silas_Sancona]

7 minutes ago, Jimbean said:

That map is trash

To some perhaps..  Accurate enough here..

[mnorell]

Please note that the mean/average is not an "expected value." It is merely a statistical average of a data-set where actual historical data-points will likely skew well above and below that value, and usually in quite an irregular distribution. Thus really not that great as a predictive tool. If you want to get closer to an "expected" value (and that doesn't exist really...even in a more predictable lower-latitude island such as Key West), you'll be better served by calculating the mode (most commonly occurring value in a dataset, say for a given date over a stretch of years) and take into account likely variation using the calculated standard deviation.

[PalmsInBaltimore]

Yes it would be helpful to have the standard deviation. Even then like you said this is only a rough tool and a very rough guide for planting purposes, as it is only an average measurement like you said. Averages are definitely useful though when there’s a large dataset such as with daily temperatures between 1995-2024.

[Jimbean]

On 7/6/2024 at 7:56 PM, Silas_Sancona said:

To some perhaps..  Accurate enough here..

Then let's see how Sabal palmetto hold up in the supposed 8A in Philly

[Silas_Sancona]

Never know until bold enough to try 

 

[SeanK]

On 7/6/2024 at 9:43 PM, PalmsInBaltimore said:

Yes it would be helpful to have the standard deviation. Even then like you said this is only a rough tool and a very rough guide for planting purposes, as it is only an average measurement like you said. Averages are definitely useful though when there’s a large dataset such as with daily temperatures between 1995-2024.

The zone temperature rating is the -3 sigma number, averaged over the years encompassed by the map. Sigma is 5F° near the coast, 7F° inland.

For my 'hood, it means that

1. 30 years of data was looked at

2. Each year, minimum temps were recorded and then those were averaged

3. So mine is approx 12°F, and the daily average minimum for Dec and Jan is (12 + 21) = 33° F

[nyy_ct]

On 7/6/2024 at 8:46 PM, PalmsInBaltimore said:

yes, definitely a continuation of the trend.

As for the uneven spread, I don't find it strange at all that the zones are rising along the East Coast faster than they are further inland. I'm looking at the 2023 USDA hardiness zones, and you can see basically the transition from the coastal plains in Delmarva, the Carolinas, and Georgia, rising to piedmont and then to the appalachians, alleghenies, blue ridge, etc. The 7a "fairly far south" in central virginia is near charlottesville and skyline drive in the shenandoah valley. almost alpine in terms of the different microclimates and shadows created by the ridge and valley geography.

As for the Florida panhandle, that is where the highest elevation in the state (a mere 100 meters/345 feet) is, so I'd chalk that one up to elevation affecting the hardiness zone.

Here in Baltimore, it is pretty unexpected how much of the city's metro area is now 8a. The fall line appears to come into play. Areas below the fall line are 8a; areas above it are 7b, and then dropping to 7a the higher up you go, and down into zone 6 in western maryland. 

Obviously areas near water are warmer. There aren't many trees in the Delmarva peninsula, and it's pretty flat. I wonder if that's why it's mostly 7b, despite being a low-lying area surrounded on three sides by water, whereas the waterfront edges of it are 8a.

Do you figure there is a pine barrens effect in DelMarVa?

[nyy_ct]

On 7/8/2024 at 8:23 AM, Jimbean said:

Then let's see how Sabal palmetto hold up in the supposed 8A in Philly

Standard Sabal palmetto is reliable in long-term (30+ years) 8B (15F expected mean) and above only. Zone by itself does not necessarily correlate to days continuously below 0C nor does it indicate the factors of dispersion, only the expected average annual min. You can have a statistical zone 8a with a higher probability of a 6b winter, due to standard deviation, over 30 years than a 7b.

[nyy_ct]

On 7/7/2024 at 12:47 AM, Jimbean said:

That map is trash

Bless your heart. 

[PalmsInBaltimore]

1 hour ago, nyy_ct said:

Do you figure there is a pine barrens effect in DelMarVa?

Are you referring to frost pockets? 

This link is interesting. Focused on growing fruit, not palms, but the frost information is interesting. From 2023:

"Another issue with fruit siting is air drainage. Our last 2 winters have had sub-zero conditions which can cause problems with winter kill in some grapes and brambles and bud damage in some tree fruits. Lower areas where cold air drains to also are more susceptible to late frost damage to flowers in the spring, particularly in peaches, nectarines, apricots, and plums. All sites should be evaluated for air drainage by doing elevations on the property. Fruit should be planted on the highest elevations and frost pockets should be avoided. Frost pockets are easily seen by looking where frost is found during late spring frost events. On Delmarva, an issue we have is that some areas are just completely flat, with low elevation. These areas will not allow for air to drain and can also have issues with cold air accumulating."

https://sites.udel.edu/weeklycropupdate/?p=21971

[RFun]

On 7/3/2024 at 7:32 PM, nyy_ct said:

Don’t shoot the messenger, some major surprises in the data but at the same time a continuation of the trend seen in the 2023 Map put out by the USDA for 1991-2020. 
 

This map is “quick and dirty” using Google earth and may trigger some climate change skeptics. It covers 1995-2024 using NowData. 

Shockingly, the Virginia Beach-Norfolk is thoroughly 8B, 8A has engulfed the entire Chesapeake, Lewes, DE popped up to a low 8B, 8A has crept up the NJ shore, parts of Long Island (La Guardia in Queens, NYC to Syosset) are now 8A, Montauk, NY on the tip of Long Island is now 8A, several stations in coastal Connecticut are now 7B (crape myrtles going “viral” now in parts) parts of the Outer Banks, NC are now 9B (Okracoke), as is Charleston, SC. Richmond and suburbs and Williamsburg in Virginia are now 8A, as is the urban core of Charlottesville, Virginia. The biggest jumps are happening in coastal areas in the middle 60% of the US eastern seaboard. Also, the Western Florida Keys are now showing 12A.

The US east coast now ranges from 5B in Down East Maine to 12A in Key West, and it appears zone 8B has become modal for many areas in the coastal region.

Strange finding 7A fairly far south in Central Virginia when it is rapidly expanding north closer to the coast.

The same finding 8B in northern Peninsular Florida when Lewes, Delaware is showing a (barely) 8B designation now. 7B appears rapidly expanding in the upper mid Atlantic/northeast and 8A in the lower mid Atlantic. If the patterns hold, where will we be in 2030? 2049?
 

Obviously, zone alone does not factor in duration of subfreezing whether, it’s only a mean (expected value) derived from a trailing set of years, nor does it indicate the variance or distribution or probability of warmer or lower cold extremes relative to that mean. There was no interpolation or smoothing of data here. I understand the limitations in usefulness and implications of data quality/availability in certain locations, and, obviously, that 2024 has not finished, but still fascinating to see in my view.

There was no data interpolation to build the map, and as I said just “quick and dirty” but I skipped over stations with clearly less than 7 or so years of data to work with.

Enjoy (or cringe). Thanks for having a look ladies and gents.

 

 

 

While the temps are trending up, I would use a longer time frame as a general guide.  Try something like 50 or 100 years (if possible).  Not perfect, but I'd rather use that as my general guide and then make practical adjustments for any cold snaps to the actual plants (if needed).

[SeanK]

22 hours ago, nyy_ct said:

Standard Sabal palmetto is reliable in long-term (30+ years) 8B (15F expected mean) and above only. Zone by itself does not necessarily correlate to days continuously below 0C nor does it indicate the factors of dispersion, only the expected average annual min. You can have a statistical zone 8a with a higher probability of a 6b winter, due to standard deviation, over 30 years than a 7b.

What does the last sentence mean?

[RFun]

23 hours ago, nyy_ct said:

Standard Sabal palmetto is reliable in long-term (30+ years) 8B (15F expected mean) and above only. Zone by itself does not necessarily correlate to days continuously below 0C nor does it indicate the factors of dispersion, only the expected average annual min. You can have a statistical zone 8a with a higher probability of a 6b winter, due to standard deviation, over 30 years than a 7b.

I disagree with this.  Sabal Palmetto can be found long term in 8a and even 7b.  It all depends on genetics and numerous other factors of the climate.

[RFun]

22 minutes ago, SeanK said:

What does the last sentence mean?

He is basically saying that it's a possibility.  It really doesn't mean much in any practical sense.

[SeanK]

39 minutes ago, RFun said:

I disagree with this.  Sabal Palmetto can be found long term in 8a and even 7b.  It all depends on genetics and numerous other factors of the climate.

We need a definition of " long term".

[RFun]

13 hours ago, SeanK said:

We need a definition of " long term".

30+ plus years was what he was using.  That's what I was going with.  That's a pretty good chunk of one's life, in all fairness. 

[SeanK]

11 hours ago, RFun said:

30+ plus years was what he was using.  That's what I was going with.  That's a pretty good chunk of one's life, in all fairness. 

I wouldn't say S.palmetto was necessarily reliable in z7b then. I guess how often it saw z7a temps.

[RFun]

9 hours ago, SeanK said:

I wouldn't say S.palmetto was necessarily reliable in z7b then. I guess how often it saw z7a temps.

It has proven to be reliable in strong areas of 7b.  And it is capable of handling a short period that would include 7a lows. 

[SeanK]

3 hours ago, RFun said:

It has proven to be reliable in strong areas of 7b.  And it is capable of handling a short period that would include 7a lows. 

A true z7b will see an occasional z7a night. My minimum from the new USDA map is 12°. Yet we saw 5° in Dec 2022. That's a -4 sigma value for my area.

[RFun]

3 hours ago, SeanK said:

A true z7b will see an occasional z7a night. My minimum from the new USDA map is 12°. Yet we saw 5° in Dec 2022. That's a -4 sigma value for my area.

Short periods of cold don't have the same impact as long periods of cold.  Wilmington, NC saw 0F in 1989.  The Sabal Palmettos pulled through fine.

[SeanK]

2 hours ago, RFun said:

Short periods of cold don't have the same impact as long periods of cold.  Wilmington, NC saw 0F in 1989.  The Sabal Palmettos pulled through fine.

Can they take it consecutive winters?

[RFun]

14 hours ago, SeanK said:

Can they take it consecutive winters?

As long as the periods of cold are short enough.

[nyy_ct]

On 7/21/2024 at 11:19 PM, SeanK said:

What does the last sentence mean?

An average or a mean is calculated off of a wide range of values, in this case annual absolute minima for a set of years (the data). Mean by itself doesn’t give us this information as to factors of dispersion. 
 

Simple ex: 

Three consecutive winters in City A and City B both have average minima of +10F. However, City A had lows of +2, +19, +9 in years 1-3 while City B had lows of +8, +11, +11 in the same period. Both are zone 8a on average, yet both are clearly not equal. There is far more variance in absolute minima in City A, which, holding all else equal, makes it likely harder for certain plants to survive the winter. 
 

https://en.m.wikipedia.org/wiki/Statistical_dispersion

 

[RFun]

On 7/27/2024 at 10:16 AM, nyy_ct said:

An average or a mean is calculated off of a wide range of values, in this case annual absolute minima for a set of years (the data). Mean by itself doesn’t give us this information as to factors of dispersion. 
 

Simple ex: 

Three consecutive winters in City A and City B both have average minima of +10F. However, City A had lows of +2, +19, +9 in years 1-3 while City B had lows of +8, +11, +11 in the same period. Both are zone 8a on average, yet both are clearly not equal. There is far more variance in absolute minima in City A, which, holding all else equal, makes it likely harder for certain plants to survive the winter. 
 

https://en.m.wikipedia.org/wiki/Statistical_dispersion

 

That's the thing with weather though.  It's open to variation.  So, the all else holding equal thing is subject to change.  As always, plant at your own individual risk tolerance.  But, also, I would recommend using common sense more than fear when making the decisions.

[RFun]

Just now, RFun said:

That's the thing with weather though.  It's open to variation.  So, the all else holding equal thing is subject to change.  As always, plant at your own individual risk tolerance.  But, also, I would recommend using common sense more than fear when making the decisions.

I'd also add that not only is the fear likely overblown with some planters, consider that you do have to ability to add protection (if needed).