Posted by Tom Philly on 11/7/2009, 6:23 pm
76.116.246.197

Went down to 38 last night in Center City. Coldest night of the fall so far. No frost damage here even on impatiens or bananas. However, evidently it went down to 32 degrees at the airport and there were scattered frosts. According to this article below, frosts are generally getting later each year and even the airport hasn't had a frost before Halloween since 1992. That said, they note at the turn of the last century, the average frost date was Nov 17. http://www.philly.com/philly/news/breaking/20091107_First_freeze_of_the_season.html Philadelphia, PA Zone 7/8

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Posted by Phil in Atlanta on 11/7/2009, 7:26 pm, in reply to "38 in my backyard but 32 at the airport last night"
99.26.112.230

Hi Tom - just wanted to clarify frost vs freeze. According to this article below, frosts are generally getting later each year and even the airport hasn't had a frost before Halloween since 1992. That said, they note at the turn of the last century, the average frost date was Nov 17. I believe the article was referring to freezes, not frosts. 2 separate events (usually). And it said, "During a 15-year stretch at the turn of the century, for example, the average first freeze date was Nov. 17." Sounds like a nice run indeed - as well as the noted recent relatively warm period, "October freezes used to be routine, but the airport temperature hasn't dropped to 32 before Oct. 31 since 1992, the longest such streak in the 136-year period of record." Generally 36F is considered a frost temp (but this various widely). I guess the thought is that at 36F frost can definitely occur. (but some have noted frosts at 40F, and others (especially out west) have noted little frost even at freezing. Below are the official Philly numbers in case you are interested. Glad you escaped the freeze/frost. Sorry about game 6. Phil Just looked this up. Per NOAA/NWS site, here is a 30 year average (1971-2000): Philadelphia Area (ThreadEx Station) First/Last Dates Minimum Temperature <= 32 degrees F Years: 1971-2000 Last First Prob 100% 100% Average Apr 6 Nov 4 ------------- Philadelphia Area (ThreadEx Station) First/Last Dates Minimum Temperature <= 36 degrees F Years: 1971-2000 Last First Prob 100% 100% Average Apr 15 Oct 26 Atlanta, Georgia January 52F/34F, July 89F/71F Hardiness z8a Annual: Rain = 50 inches, GDD's = 5300 Winter low last 6 years: 12F, 15F, 18F, 24F, 16F, 18F

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Posted by Steve NJ z7a on 11/7/2009, 7:53 pm, in reply to "Re: 38 in my backyard but 32 at the airport last night"
72.82.178.198

Temperatures were taken in the city before the airport was built. This needs to be considered when comparisons of temperatures between 1900 and the present are made. Center city Philadelphia sometimes can have impatiens until early to mid December.

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Posted by Jim Wilmington DE 7a on 11/7/2009, 10:48 pm, in reply to "38 in my backyard but 32 at the airport last night"
173.49.190.17

My Fig Tree is my best barometer of frosts/freezes (besides my thermometers). Last night was the FIRST night that I took any damage to Fig leaves. There were maybe 7 to 10 that were moderately curled up and toasted. The rest of the tree showed "normal", undamaged leaves. ...Although, about a third of the tree has turned yellow simply due to autumn. And it was the yellow leaves that took damage (from this morning's cold) the most. My point is, the damage I saw was VERY CONSISTENT with a 34F low, but not consistent with a 29F low. Had my Fig tree seen 28.9F, I'd fully expect almost all the leaves to be crinkled up today. Micro-climates are real. Jim, Wilmington, DE, 7a Last 30 Years Avg. Winter Low: 5.27F Last 10 Years Avg. Winter Low: 8.6F Favorite Palms: Species: Phoenix Canariensis / Genus: Sabal Other Loves: History, Music, Baseball

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Posted by Terry 6b7a NJ on 11/8/2009, 1:11 am, in reply to "34F in My Backyard, 28.9F at Wilmington Airport"
12.145.92.22

Finally had first freeze here!...But 70 deg. coming right up! Just one (kind of) wintery day, now it's back to normal (or even above normal). But glad some of you (Jim) were still just above freezing last night. Late last night had reached around 29 here anyway. Still a mix here as some plants have still held their green, even a wysteria vine, with even some annuals still flowering (though fewer), with some fall colors, and other trees/bushes past peak. So it doesn't really quite "look" like November yet, but that will change a lot by the end of the month (perhaps). This talk of first freezes and frosts and record-keeping makes we wonder again about these dates and numbers. As someone pointed out, they took some of those temp. readings before there was even an airport there. And even though Philly was a big city for that time, look how much it's grown and the sprawl. Don't know if they had many concrete sidewalks then (I think perhaps wooden), and streets weren't paved, mainly cobblestone or dirt, right? Even temperatures taken within the city limits back then I'm sure weren't quite the heat islands they are today, not to mention heat from cars, trucks, buses...etc. I'm glad we have those records from back then, but is there really enough weather data today that mimicks how the data was collected back then? Only then would it really seem we'd have a more accurate depiction of weather data and changes over time. Rainfall 50" per year - Elev. under 250 ft. 22 miles west of downtown Manhattan Lowland wooded swamp- Remnant glacial swamp(meltwaters)from Ice Age State Dinosaur: Hadrosaurus Foulkii(plant-eater)

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Posted by Jim Wilmington DE 7a on 11/8/2009, 4:06 pm, in reply to "Re: Virtually the same here, but still greens, browns, and mixed colors...also airports, cities,..."
173.49.194.192

Terry, Interesting and well thought out comments on urban sprawl and its relationship, historically, to temperature data. When I saw the 28.9F reading at Wilmington, and compared it to my own reading, some 5.1 degrees warmer, it just makes me crazy. When I see with my eyes the very nominal damage to my Fig tree's leaves (fig leaves are very sensitive to frost), I know the temperature in my yard was closer to 34F than 29F. Moreover, when I look at the hourlies as posted at WeatherUnderground, I often (on many nights) see crazy anomalies. I can see a temperature hold steady for three hours overnight, bump UP 2 full degrees for one hour, then bump right back down to where it was. What would cause that in the middle of the night? Then there's the hourlies of Saturday morning: 12:51 ~ 30.0 1:51 ~ 30.9 2:51 ~ 30.0 3:51 ~ 30.0 4:51 ~ 30.0 5:51 ~ 30.0 6:51 ~ 28.9 7:51 ~ 34.0 Now, even trickier, is that our low for the day is officially listed as 27F! Just where they got THAT number, I don't know. Only the hourlies should count, although I've heard that if the lowest number is recorded between the hourlies, it will get duly noted, though not appear as an hourly reading! Sounds like hocus-pocus to me. Anyway, I've had issues with Wilmington's readings and tried to look at other area lows for Saturday morning, but the closest NOAA/NWS weather stations are all too far away to be germane to the issue. I think the closest stations are Philly and Trenton to the north, and Dover to the South. I would've thought Elkton, Aberdeen or Northeast (a town), Maryland, would have an NWS station, but they don't show up. The nearest Maryland station is Annapolis or Baltimore! Now, I CAN find non-NOAA/NWS stations all around Wilmington. And their temperatures vary WILDLY. But we're talking grade school weather stations and the like. All the integrity of a bank time & temperature sign! What I need on a night/morning when I see a questionable (or record) number come in from the airport is good concurrent data from Newark, Delaware City, Chester, PA, West Chester, PA (nowhere near Chester, incidentally) Pennsgrove, NJ and Elkton, MD. With good numbers from those places, a wacky reading from Wilmington could either be underscored and supported, or discounted and discarded. Jim, Wilmington, DE, 7a Last 30 Years Avg. Winter Low: 5.27F Last 10 Years Avg. Winter Low: 8.6F Favorite Palms: Species: Phoenix Canariensis / Genus: Sabal Other Loves: History, Music, Baseball

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Posted by Phil in Atlanta on 11/8/2009, 5:10 pm, in reply to "Re: Virtually the same here, but still greens, browns, and mixed colors...also airports, cities,..."
199.67.131.152

Just where they got THAT number, I don't know. Only the hourlies should count, although I've heard that if the lowest number is recorded between the hourlies, it will get duly noted, though not appear as an hourly reading! Sounds like hocus-pocus to me. Jim, many official sites of cities do not just record hourly observations. Atlanta records the lowest temp period regardless of the hourly observation. Many official sites record ALL temperatures observed regardless. Others sites only record observations on each hour. And still others only record hourly observations from around 7am to 10pm. It just depends on staff and budget I guess. Phil Atlanta, Georgia January 52F/34F, July 89F/71F Hardiness z8a Annual: Rain = 50 inches, GDD's = 5300 Winter low last 6 years: 12F, 15F, 18F, 24F, 16F, 18F

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Posted by Jim Wilmington DE 7a on 11/8/2009, 5:56 pm, in reply to "Temp recording sites"
173.49.194.192

> It just depends on staff and budget I guess. < Phil, Isn't weather recording all done automatically these days? I wouldn't think that there's too much human involvement in 2009. If for nothing else than the tested and true business practice of, "Why pay somebody to do something that I can get a machine to do for free?" My vision (perhaps very off-base) is of mechanized/computerized weather stations that "phone in" all their information to collecting stations or hubs. It then goes from there to the NOAA/NWS/WU/weather.com sites, then to our monitors -- with very little human involvement. Not true? Jim, Wilmington, DE, 7a Last 30 Years Avg. Winter Low: 5.27F Last 10 Years Avg. Winter Low: 8.6F Favorite Palms: Species: Phoenix Canariensis / Genus: Sabal Other Loves: History, Music, Baseball

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Posted by Phil in Atlanta on 11/9/2009, 7:51 pm, in reply to "Re: Temp recording sites"
99.26.112.230

Jim, I actually have no idea. But the reason I said staff/budget is maybe they do not have the up-to-date automated equipment? Or the manpower to monitor/maintain it? I dunno. But to this day there are many sites that only record hourly observations, and some that only do so from 7am to 10pm or whatever. Maybe thats just all they choose to report, who knows. Phil Atlanta, Georgia January 52F/34F, July 89F/71F Hardiness z8a Annual: Rain = 50 inches, GDD's = 5300 Winter low last 6 years: 12F, 15F, 18F, 24F, 16F, 18F

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Posted by Tom Philly on 11/9/2009, 10:53 pm, in reply to "Re: 38 in my backyard but 32 at the airport last night"
208.180.142.69

Yes frost and freeze are different. Frost is definetly influenced by the interplay of temperature, wind and humidity. I think they were refering to temperatures of 32 or below in the article. The heat island of cities like Philadlephia and New York are much different than those of sprawling cities like Houston or San Jose which are much more suburban and whose city limits seem to go on forever and ever. I remember some years in Philly when I would see annuals like Begonia semperflorens in windowboxes and planters around the city still alive at Christmas. They hadn't frozen yet and were sort of just in limbo. Like being in a refrigerator with light for a few weeks! Other years of course we had several hard freezes by Christmas and all of the annuals were toast. Philadelphia, PA Zone 7/8

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