March (Weather) Madness
Some folks in North Georgia got an unusual late March sight: snow flurries fell briefly this afternoon. Although it was 45 degrees outside, much colder air aloft combined with lower pressure caused by a short wave passing through squeezed out just enough moisture for the flakes, which melted on contact with the ground. Temperatures today are 20 degrees cooler than normal, and the northern two thirds of the state will see a freeze tonight. If you succumbed to the spring planting urge over the weekend, either bring your plants in, or at least cover them over.
Tonight’s freeze won’t be anywhere near as bad as the Easter Freeze of 2007. though. Not only is it likely to be a bit warmer than the 28 degrees recorded last April, but not as many plants have started to bloom. A freeze in late March isn’t too unusual. For metro Atlanta, the typical last frost occurs sometime between April 1st and April 15th.
Communities along the Ohio and Mississippi Rivers are suffering through one of the worst flooding seasons in years. The map below shows the potential for flooding this spring in the United States, according to the Spring flood outlook:
The heavy snowfall in Ohio is partially responsible for the current round of flooding, while up in the Northeast, record snowfalls in New Hampshire, Vermont and Maine increase the flooding potential once the snow melts. Of course, here in Georgia the drought has limited the potential for any flooding according to the Georgia Flood Outlook.
The Weather Service has updated its report from the March 14th tornado that struck downtown Atlanta. New estimates show wind speeds of about 120 mph when the twister passed over the World Congress Center, compared with the original estimate of 100 MPH, and traveled slightly further than what was originally estimated. The storms the following day are now estimated to have caused three tornadoes instead of two, according to the updated damage report. The third tornado occurred in Butts County, south of Atlanta.
And finally, there is at least one Australian scientist who thinks that global warming is over, and the earth is now entering a cooling phase. The peak of global warming actually occurred in 2000, and for the last eight years, the trend is towards cooler weather.
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March 25th, 2008 at 11:50 am
According to weather sites the temperature did drop to 26F this morning.
How long does the temperature need to be in the 20s to kill flowers on a peach tree for example?
March 25th, 2008 at 6:53 pm
Indeed the temperature dropped below freezing for much of North Georgia. While the ‘official’ gauge in Atlanta showed 30 degrees, four above the record of 26, I got down to 26 here in Lawrenceville, Peachtree DeKalb dropped to 27, Athens was 28, and it appears the lowest temperatures were recorded in Rome (24) and Peachtree City (23).
It looks like temperatures didn’t drop below freezing until about 2:30 AM, and stayed below freezing for six hours or so. Looking around the yard this afternoon, it looks like there was some damage to new azalea leaves and some flowers that were fully formed. There was also some damage to the hydrangeas, although not a lot. Some plants that were damaged in last year’s freeze escaped unscathed, including the grape hollies.
As far as your question about damage to peach trees, I found some research from the Alabama cooperative extension service that said for flowers in full bloom, there is 10% damage if the temperature is between 27 and 28, while there is near 100% damage if the temperature drops to 26. If the flowers aren’t in full bloom, the temperature can drop to 25 for 10% damage, and all the way down to 18 before there is 100% damage. Of course, they are talking about commercial trees for fruit production, not the ornamentals we see in the landscape, but I think this gives some idea of where the temperatures have to be to damage flowers at a given level of development.
Taking a look at today’s news, it appears that up at Jaemor Farms in Lula, temperatures dropped as low as 21, but the owners say it looks like there might be only 10% damage to the crop. I guess most of his trees were still in the budding stage.
Worries about cold weather will likely fade into memory. After some cool but still above freezing temperatures tonight, we’ll get back to normal (and even above normal) by the weekend, and I don’t see another below freezing night at least for the next two weeks.
April 4th, 2008 at 10:09 am
As an update, our peach tree had only minor damage, so I guess it was not in full bloom yet. Pear tree is a little hardier than peach, so it did fine too. So we should have some fruit this summer and fall.