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Are the zones still the same?


Palmy
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As many of you know, there has been a very cold freeze in the west. My question is do zones change becuase of it getting so cold. After this freeze am I still zone 9b, considering it was 21f? I hear it was in the mid/upper teens in the 1990 freeze and the zones did not change. As much as I would love to say Im 9b, its very hard to grow 9b species here. Still 9b? 4 days of under 25F, 3 just recently and 1 earlier this year.

Meteorologist and PhD student in Climate Science

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Zach-

The zone maps are based on taking the average mininum low for a given area overa certain number of years.  The number of years depends on the the map and waht data period was employed.  As such, one zone busting event doesnt mean your average wont still fall into the 9b category.

But, one must take into account that just because the map say zone "X", it doesnt mean temps of less than that zone cant occur.....it just means that the average falls within the range defined by that zone.

This problem is probably more pronounced here in the east than in California as we can go a long time without a zone buster freeze....but when we bust zones....we bust zones :D

Larry 

Palm Harbor, FL 10a / Ft Myers, FL 10b

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I am beginning to not put too much stock into zone maps. I am just trying plants and seeing if they work. Also, I try to look for big specimens of various cold tender plants and plant those if I like them. For example, Ficus sp. and Dypsis lutescens seem to thrive in my immediate area so I planted these. That is not to say that I am not trying other goodies like coconuts, V. arecina, Hyophorbe sp.  In other words, be sure to plant whatever you see in your area that looks good, is big and is flourishing, then experiment with other stuff you don't mind losing. As far as a California 9B compared to a FL 9B (like where I am), it looks like California has a tendency to linger longer below freezing for more days compared to what would happen around here. I should go into the 28 to 29 degree range once or twice a year on a given radiational night, but the duration below freezing is likely to be much shorter than what you just experienced in CA, and I am likely to rebound very quickly in the morning to probably 60 to 65 degree range with 27.7 degree south latitude full sun beating down all day (likely to be clear after a radiational cooling event). Now, the freak advective freezes of the 80's were a different story as we may have spent a long time below freezing with little sun the following day with little temperature rebound. And throwing frost (which I am more likely to get than CA) complicates matters worse. It only got down to 30 or 31 degree F in ruskin, FL last Feb 14, but there was a wicked frost that may have defoliated or even killed palms I have in the ground now - and an ultimate low of 31 degrees for a year around here is pretty warm. Palmy, everyone's zones probably still stand in California, this was just a rare freeze for you guys. Ours will come eventually in time. I've read on other posts through all of this that the redlands area of sout FL saw temps to high teens to low 20's F during past freezes and this area is one of the most mind boggling beautiful, tropical looking places I have been - and I just took a trip to Hawaii. The palms down there look flawless! And someone can correct me, but I think that part of florida may have seen a light frost in November 2006 - yet nothing looks damaged because it got up to like 70 degrees f the next day. Sorry for the long post.......

Parrish, FL

Zone 9B

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Correct me if I'm wrong, but 9b would be an average minimum low of 30F, 9a/25F, 8b/20F, etc..  Right?

Steve

USDA Zone 9a/b, AHS Heat Zone 9, Sunset Zone 28

49'/14m above sea level, 25mi/40km to Galveston Bay

Long-term average rainfall 47.84"/1215mm

Near-term (7yr) average rainfall 55.44"/1410mm

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Steve, I think it is a range. 11 ~ 40+, 10B 35-40, 10A 30-35, 9B 25-30, 9A 20-25 and so on...

5 degrees F is a large range - Big difference in a 9B that has a low average of 29.5 F compared to one that has a low average of 25.5

One can have a pretty interesting palm garden if they are on the high side of 9B and a very expensive one if they are on the low side of 9B. To make matters worse, the recent zone maps did away with the A/B gradations making the range 10 degrees F which can be pretty useless in some areas. New maps have me in Zone 10 - but it clearly must be a 30 degree zone 10 at best. In reality, I looked back at about 6 or 7 years worth of data from the Ruskin NWS office which was the amount easily available for free on line. I think the lows  averaged out to around 29.6 F for that short period of time so I still claim the 9B designation as it keeps me honest. There have been very nasty freezes here in the past and it is only matter of time. Good news (or bad news really) is that the freeze that busts my zone will likely bust everyone's zone in west central FL. This freeze will be advective in nature and turn zone 10 palms into mush from Pineallas county all the way to maybe as far south as Lee county. So really, the more solid zone 10 areas around me (like st. pete, sarasota, fort myers) are going down with me unless they are within 1/2 mile of the coast or are in a really super microclimate. West coast barrier islands are the only truly safe places in FL (they are pretty safe on the east coast too, but maybe a bit more susceptible to advective freezes at the same latitude as the west coast barrier islands). Sorry for another long post.....

Parrish, FL

Zone 9B

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Thanks for the insight  :D

This freeze tested the extent of how much influence the ocean provides. Every night of this freeze which started last Thursday 1-11-07 in NorCal & Saturday in SoCal. there were remote coastal & foothills locations above 40F surrounded by areas below freezing.

Chronology of the freeze:

Minimums:

>>>>>>>>>Thurs >>Fri >>Sat > Sun >Mon

San Francisco 40F >40F >> 39F >>37F >36F    

Los Angeles > 55F  47F  >>39F >>36F > 36F

San Diego >>51F >52F >>45F >>36F >35F

These temps are almost laughable compared to what occurred within mere miles of these weather stations, esp in the Bay Area & San Diego county. Los Angeles basin remained above freezing but valleys dropped into the 20's.   :(

Now I really appreciate zone 11  :P

Los Angeles/Pasadena

34° 10' N   118° 18' W

Elevation: 910'/278m

January Average Hi/Lo: 69F/50F

July Average Hi/Lo: 88F/66F

Average Rainfall: 19"/48cm

USDA 11/Sunset 23

http://cdec.water.ca.gov/cgi-progs/queryF?MTW

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(ruskinPalms @ Jan. 15 2007,21:34)

QUOTE
Steve, I think it is a range. 11 ~ 40+, 10B 35-40, 10A 30-35, 9B 25-30, 9A 20-25 and so on...

This is correct, if you are a 9B, your average winter low is somewhere between 25 and 30F.  Could be lower, could be higher some years, but that is the average.

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(spockvr6 @ Jan. 15 2007,23:15)

QUOTE
Happ-

I thought I saw that San Fran AP logged 32F?

You did see that Larry but the airport isn't even in San Francisco county.  Though influenced by the bay the airport doesn't reflect San Francisco city [Mission Dolores] near total marine climate.  There are neighborhoods [like the Sunset District] that are engulfed by fog all day in summer & barely 60F.  The city of San Francisco & adjoining Pacifica stayed in the mid 30's-low 40's during this freeze.

Los Angeles/Pasadena

34° 10' N   118° 18' W

Elevation: 910'/278m

January Average Hi/Lo: 69F/50F

July Average Hi/Lo: 88F/66F

Average Rainfall: 19"/48cm

USDA 11/Sunset 23

http://cdec.water.ca.gov/cgi-progs/queryF?MTW

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Bill

I did the same calculation using NWS data and came up with a 29.625F minimum average for the last eight years (all the historical data they had) at the Hobby Airport weather station which is the closest I can find to my location.  I did notice that Hobby recorded 28F in 2004 - I didn't quite freeze that year.  Also, Hobby recorded 32F in 2006 - I didn't freeze last year either.  So there are some anomalies generated by all the concrete that surrounds me.  All things considered, that would seem to make me a solid 9b.

Four of the local tv stations have the worst case low (tomorrow night) at 30F, the Weather Channel has us at 31F, and Weatherunderground at 29F.  So, I guess despite all the histrionics we Texans are displaying due to the freezing precipitation, this event is definitely in the "normal" or "average" temperature range.

Steve

USDA Zone 9a/b, AHS Heat Zone 9, Sunset Zone 28

49'/14m above sea level, 25mi/40km to Galveston Bay

Long-term average rainfall 47.84"/1215mm

Near-term (7yr) average rainfall 55.44"/1410mm

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Yeah, but we aren't warming up at all during the day either.  I am supposed to get down to 29F in San Antonio,  not bad, but stay in the 30s all day tomorrow, with a mixture of precip, rain and sleet, possibly ice.  Very unusual that daytime highs are so low.

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