"This rainfall was good, but it’s not enough to be a large-scale drought buster,“ climatologist says
DES MOINES — For some Iowa farmers, much-needed weekend storms held the hope of a fabled billion-dollar rain that drenched their fields — but drought-parched regions in crop-rich northern counties got little or nothing from threatening skies that never delivered.
Rainfall amounts varied significantly across the state from Sunday’s storms, with 3 to 4 inches reported in parts of northeast Iowa and across some of the state’s southern counties, along with some hail and high winds confirmed as tornadoes striking Jackson and Dubuque counties and Marion County. But State Climatologist Justin Glisan said there was considerable precipitation drop off in northern areas, where severe drought conditions persist as corn and soybean plants are developing.
"This rainfall was good, but it’s not enough to be a large-scale drought buster. We would need regular rainfalls to meet the climatological need for several months to actually bust the drought," Glisan said Monday — the official start of astronomical summer. "This time of the year in late May to June, we would typically need an inch of rain per week to meet the climatological expectation, given that May and June are the two wettest months for the state."
The state climatologist and other weather forecasters said they expect a significant, short-term shake-up in the atmospheric pattern to usher cooler, wetter conditions into Iowa moving into July — and with that additional rain could come more violent thunderstorms as the trade-off to get that needed precipitation.
But come hail or high water, there are parts of Iowa in need of more rain. Southeast Iowa the only area of the state without drought conditions, according to the most recent U.S. Drought Monitor.
Glisan said the weekend rain was beneficial to parts of Iowa, where 76 percent of the state is experiencing moderate severe drought conditions.
"If you put it in the context of June being the wettest month, for the northern two-thirds of the state and the first 15 days we started out with a statewide average of 0.2 inches when it should have been about 2.5 inches at that time, I would say that this is a billion-dollar rain," he said in assessing Iowa's weekend weather. "These timely rainfalls really do put a dent in moisture stress, but we had some field agronomists saying that even with the rains that we’ve had over the last week they were still seeing corn rolling in the morning in those drier areas. So, while it’s much-welcomed rainfall, we need consistent rainfall moving forward.“
Mark Licht, an assistant professor of agronomy at Iowa State University, said he wasn't ready to put the latest rainfall event in that "billion-dollar" category "largely because there was not large enough rains across a large enough area," especially in Iowa's major crop-growing regions." However, he added "it’s a start. It’s well-appreciated, but depending on where you were and how much you got, it really has not subsided the drought concerns as far as crop conditions."
At the same time, Licht said having rainfall in Iowa had value in that the moisture provided "just a little bit of hope" for farmers who are feeling some angst and anxiety heading into a key developmental period when corn plants are initiating ears and filling in kernels until pollination hits in mid-July — factors that all could impact the 2021 crop's yield potential. Soybean plants, he added, are better able to adjust and compensate for environmental stress.
"The next couple of weeks here — cool weather, more precipitation, that bodes well," he said. "Any drought stress has the potential to lower our yield potential."
A weekly crop report released Monday by the U.S. Department of Agriculture noted that farmers “reported corn curling and ground cracking in some areas.” The report found that Iowa’s corn condition rated 56 percent good to excellent, a drop of 7 percentage points since the week before. While the emergence of soybean plants is ahead of normal, the percentage of plants considered to be good to excellent declined, the report said.
Farmers, for the most part, are taking things "in stride" as they wait for their crops to develop and watch the sky, said Licht, who travels Iowa to monitor crop development. "They understand the situation and, unfortunately, in this situation there’s just nothing they can do about it," he said. "There’s a little bit of anxiety about what the true yield impact is going to be and, unfortunately, I don’t have the answer on the yield impact right now. The true test will be in about four weeks from now."
Both Licht and Glisan report there have been lingering effects from last August's derecho, which damaged millions of crop acres as it cut a swath across central and Eastern Iowa. Stalks of "volunteer" corn can be seen in many recently planted fields.
"It’s been interesting this year. We’ve had a lack of severe weather, and that goes hand in hand with dry conditions. If you don’t have thunderstorms to create severe weather, you don’t have thunderstorms to create rain and that’s when we start to see precipitation deficits stack up," Glisan said.
"I’m cautiously optimistic moving into this week that if we do receive measurable rainfall we could see a pattern shift in which we do get into more active behavior," he added. "Hopefully, we get those efficient rainfalls of a few tenths of an inch per hour in thunderstorms — but not strong or severe. But I guess that’s the risk we take this time of the year."