It looks like Old Man Winter is going to take one more shot at Georgia over the next few days, and that could be bad news for gardeners and farmers across the state for a second year in a row. The Weather Service is calling for low temperatures in Lawrenceville of 36 degrees on Sunday night and Tuesday night, and 34 degrees Monday night. Across the state, lows are expected to be in the upper 30s Monday morning, and 31 in Atlanta, 32 in Athens, and 30 in Macon on Tuesday morning.

Accuweather.com is calling for lows of 34 on Sunday night, 30 Monday night and 39 Tuesday Night, while Weather.com says it will be 36 Sunday night, 31 on Monday and 33 on Tuesday.  In comparison, temperatures dropped to 28 degrees the nights of April 6 and 7, 2007, the infamous Easter Freeze that caused widespread damage to spring flowers and crops.

My guess is that the damage won’t be as bad as what we saw last year– it looks like it will be a little warmer– but I wouldn’t suggest you plant any annuals this weekend.  You should also bring in any houseplants or container plants you’ve set outside until at least Wednesday. If the worst does happen, Walter Reeves has a good article on coping with freeze damage.

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Although Georgia’s drought isn’t over yet, Governor Perdue announced some loosening of watering restrictions today that will take effect on April 1st. The changes were made to help the landscaping industry which was facing a very bleak year if the current no watering at all ban remained in place. The changes also resolve the question of what to do about swimming pools this summer. (more…)

With Spring officially arriving tonight, and the weather warming up, it’s time to start thinking about planting outdoors. There are two weather-related things to keep in mind before you run out to the garden center to pick up those summer annuals.

The first is the last freeze date. You don’t want those newly planted flowers to freeze. For Georgia, the last frost date ranges from March 20th along a line from Columbus to Macon to Augusta to April 20th up in the mountains of Northeast Georgia near Clayton. According to the Weather Service, metro Atlanta to Athens has its last freeze sometime between March 30th and April 10th.

In reality, though, the last time Atlanta had a spring freeze in April was back in 2000, and before that, you have to go back to 1992. There have been a number of freezes in late March, however. In addition, Atlanta tends to be a bit warmer than the suburban counties, so the actual last freeze date would be a bit later here.

In addition to thinking about the last freeze, consider the soil temperature before you plant. Most annuals won’t grow much until the soil temperature remains above 60 degrees, and some plants, prefer temperatures above 70. I keep track of the soil temperature with a probe about 6 inches down in my backyard. A graph of the temperature is below:

The image above is live, and as I look at it, I see the soil temperature reached 56 degrees during last week’s warm spell, then dropped to 48 over the chilly weekend. It’s now on the way back up. So, as of today, it’s still too early to plant, even if you were positive we weren’t going to see any below 32 degree weather. When you see the temperature above 60 and staying there, that’s a pretty good indication that it’s safe to plant.

With temperatures recorded at Hartsfield Airport in Atlanta 4.5 degrees above normal for December as a whole, and 8.9 degrees above normal for the first six days of January, one could be forgiven for asking, “What happened to Winter?”

Even Mother Nature seems confused. Looking around the yard, I have a few daffodils blooming, the Lenten Roses have bloomed, and I even see that the Daphne is beginning to bloom. On Ronald Reagan Parkway, the Pussy Willows are coming out. All of this is about a month ahead of schedule. In New York City, the entire month of December went without any measurable snowfall–the first time that has happened since recordkeeping began.

The US has been in what’s called a split flow jet stream pattern for the last month or so, with the northern jet stream moving west to east across the northern states, and the southern jet stream moving across the southern states. The effect of this is to keep all the cold Canadian air north of the border, and to bring fronts across the Gulf of Mexico, which is what we saw with the Christmas Day storms, which brought tornadoes to central Florida, and yesterday’s storm, where a violent squall line brought an F1 tornado to the McDonough area, and rain across much of Georgia around lunchtime.

This benign weather pattern will break down by the Saturday the 13th, bringing cold air out of Canada initially into the Plains states, and then moving further east. For the week of January 15th, the Atlanta area will be lucky to see high temperatures of 50 degrees. Beyond then, we’ll likely see more typical winter weather through February.

Before then, we’re going to get two storms. Rain tomorrow could bring 1.5 inches to the area, as a front will stall over Georgia during the day. Things clear out for the work week, with somewhat lower but still relatively warm temperatures and nice weather until next weekend, when another front ahead of the colder air again brings the possibility of rainfall.

So, if your outdoor plants seem a bit overeager, don’t worry too much. There will be plenty of colder weather to slow them down.

This weekend, the Atlanta area measured the lowest temperatures in nearly two years. Here in Lawrenceville, we got down to 17.6 degrees early Saturday morning, while at Hartsfield Airport, the temperature dropped to 19 degrees. The last time the temperature dropped below was back on January 24th, 2005, with a low of 14.6 degrees.

The weather service in Peachtree City says that temperatures dropped to 5 degrees in Blairsville this morning, which is believable, and to two degrees in Thomaston — between Columbus and Macon, which is not.

The low temperatures bring to mind a discussion that has been going on among the people that decide the plant hardiness zones. Georgia is split between zone 8, which sees winter low temperatures between 10 and 20 degrees, and zone 7, where lows range between zero and 10. Atlanta is in zone 7B, defined as seeing a low temperature between 5 and 10 degrees each winter.

It’s a big deal to gardeners, since there are many plants that will survive with temperatures as low as 20 degrees, but will die if the temperatures drop to 10. We may very well see a change in hardiness zones sometime in the near future to reflect this. (The real problem with plant survival in Atlanta is the humidity and temperatures over 70 degrees on summer nights, which is a discussion for another day.)

At any rate, temperatures below 30 degrees may be few and far between for the next ten days or so, as we see a bit of a warm spell for December. Increased moisture due to a southerly flow of the jet stream will bring temperatures spanning only 20 degrees or so, from the 40s to the 60s, as opposed to the 35 to 40 degree change between morning lows and afternoon highs we’ve seen so far this month. The moisture is also likely to bring some welcome rainfall, beginning as soon as Tuesday afternoon.