Determine Your Coldhardy Zone

[osideterry]

The common zone maps weren't quite detailed enough for me, and I had to get the real info. My low temps always lined up closely with my zipcode at weather.com. I wanted to find out what my winter lows were historically in order to really know what to expect as an average. After digging around, weatherunderground seems to have the info I was looking for.

Here's the first step: Go to weatherunderground.com, and type in your zip code, city, or even closest airport code.

I hi-lited the important boxes to fill with a yellow box

[osideterry]

Next step: You are on your local weather page. Scroll down until you see "Detailed History and Climate". Select December 1, 1999. That's as far as this site goes back with data for my area. For you they may go back farther... who knows.

[osideterry]

Next step: You are at December 1, 1999. Now click on "Monthly".

[osideterry]

Now you're just getting started. From here a fella could waste a lot of time clicking through every month for the past 8 years. I just looked at December-February of each Winter.

January, 2000... 27F. Crap.

But hey, in 2003 my low temp was 36F. It's not always cold here.

[bgl]

Terry,

This is a great site! Even shows earthquake activity (there was a minor one up in Volcano Village today - had no idea!). But did you really mean 1999? When I check it for Hilo it goes back to 1949! I can check the present conditions for Pahoa (which is a few miles away from me) but there doesn't seem to be any historical data for Pahoa and I'm not surprised. Hilo works fine. And Dec. 23, 1949 was a REAL cold day. It dropped to 56F that morning in Hilo, which must be close to an all time record low. Well, the morning was cold - it actually went up to 77F by that afternoon.

Bo-Göran

[osideterry]

If I try to go before November, 1999 it says "No Data Available". Same with Camp Pendleton, the weather station next closest to me. There is a a station at the Oceanside Marina, but it has nothing in common with my microclimate. It's low last January was 10F warmer than mine.

[sonoranfans]

Great site terry, found a measurement site that appears to be very accurate for my house 1 mile away(as compared with this mornings low of 51 deg F, which was 5 degrees cooler than phoenix).  

I looked up the coldest day here in the last 30 years, jan 15, 2007.  Its really interesting that my bismarckia saw 9 hrs of sub 26 F degree F weather( the commonly rated hardiness) with a low of 20.3 deg F.  There was  virtually zero wind the whole time on january 15, 2007.  The tenth hour the temps went from 24.7 F(9am) to 35.6F(10am) as the sun warmed things up towards a 55F high that day.  Now I understand in more detail what happened on that day when my bizzies were defoliated, but survived.  I also know of a royal 5 miles away that I looked up the temps for.  It endured a very similar (+1 degree overall) fate and was defoliated and survived.  It looks nice today with 4 new palms plus a spear.  Apparently the low winds had something to do with the survivability as the wind chill was nonexistent at 0mph winds.  That royal was not near a building and had no overhead canopy.

[MattyB]

Cool Terry thanks.  

It shows my zipcode hitting 27F this January as the coldest temp they have on record.  No other recored went below freezing.   I wonder where this station is located or how they get their records.  If it's from the Fire Station where NWS gets theirs I'd be about 10 degrees warmer on those super cold nights.  Interesting.

[osideterry]

Hi Matt. You are going to have to go by your own readings starting this year for your lofty location. You going by the fire station would be like me going with the marina numbers.

Here's some info to chew on:

During my 2 warmest winters (2002-2003 and 2004-2005) my average min temp was 34F and I averaged 15" of annual rainfall.

During my 2 coldest winters (1999-2000 and 2006-2007) my average min temp was 26F and I averaged 3.5" of annual rainfall.

[galveston1602]

wunderground is a great site, I actually upload my weatherstations data to their site

http://www.wunderground.com/cgi-bin....y=77554

I have taken the average lows from their site from I think 1944 and weve definetly increased about a zone in the last 10 years... of course, any day now we could get another 25 degree year and reset us...

[happ]

Thanks for the weather nerd candy    Terry

It helps to map zone 11 like Sierra Madre Canyon/San Rafael Hills.  The night time data shows the temps rise & lower in the wind.  ::

[osideterry]

Happ - You and I are coming at this thing from opposite ends. You seem to be looking to identify Zone 11 in SoCal, while I'm trying to understand what Sunset calls Zone 22. Cold drains. One year I'm in 10b, the next I'm in 9a.

An interesting pattern I had a hunch existed, and now have evidence for:

We have 3 kinds of Winters in SoCal (my numbers, yours will vary)

1) Off-Shore Dominant (La Nina?): Low minimum temps (25-29F) and minimal rain (under 5")

2) Intermediate Influence: Moderate lows (30-31F) and medium rain (6-10")

3) On-Shore Dominant (El Nino?): Mild lows (32-36F) and heavy rainfall (over 11")

I swear, there was never an exception to the rule. If we get above average rain, we will have an above average min temp that year. If we get below average rain, we will get nasty-a$$ low temps.

I'm just an armchair weather nerd, so shoot my theory down please.

[happ]

Terry

From one "armchair weather nerd" to another  :laugh: your formula appears correct.

During wet/El Nino winters the moisture is mostly from the subtropics.  Clouds/high relative humidity/rain keeps night temps relatively warm [mostly 50's] and mild days [70's].  Rainfall can be quite heavy but mostly sporadic so that there are periods of sunshine.  The hillsides become lush & bugs [ie mosquitoes] flourish in winter.

La Nina can also be warm due to lots of sun & wind but as you point out, the possibility of cold nights can be troublesome in the dry air.

I have studied the phenomena of the cold air basin effect in northern San Diego county.  It appears the drainage off the nearby mts [san Marcos/Santa Margarita] settles over the coastal plain around Oceanside.  Without wind to mix the air the result is colder night temps [at least 10 degrees F colder than San Diego  

[bubba]

Terry, Thank you for the interesting site.

[JBa3Fan]

On the East  Coast it seems to be  reversed for us in the summer.

When we are drier than normal during the summer our temps soar to reccord highs.

What is that going to do for our low temps this winter?

I planted a bunch of Needles, Minors and Tracies this summer and am hoping for an above normal winter. (with my fingers crossed)