What's the weather outlook as we move into the 2014 harvest season? Elwynn Taylor, Iowa State University Extension climatologist, noted on September 15 that there were a few sprinkles in central Iowa and into northern Iowa and Minnesota. "But this light rain is diminishing. There will be another chance for rain later this week. As time goes by, chances of rain are getting smaller and chances of changing to warmer than usual weather for this time of year are getting larger. By the end of September, we should be in good drying conditions that will make farmers who are harvesting in Iowa happy."
Did we have a hard freeze in Iowa this past weekend? "We did in only a couple of spots, and that was Saturday morning September 13," says Taylor. "None of our weather stations in Iowa listed any 28 degree reports. We consider 28 degrees F at the weather stations as a hard freeze or killing freeze. We had a couple of 32 degree readings in the state and quite a few stations reporting lows overnight in the 33 and 34 degree range, where people could see frost on rooftops of sheds or buildings. But the glass didn't have frost on it. It had dew. When dew is forming, frost isn't forming; it wasn't quite cold enough. There was enough heat in the ground which was counter-active to the cold air that moved in overnight."
It's been so wet that the tiles are running in Iowa fields
August and early September were wetter than normal this year in Iowa. Taylor says he hasn't yet analyzed the data on rainfall for all locations around the state for that entire period. "But we have had a couple of weeks that were definitely above average in rainfall statewide," he notes. "In fact it's been so wet in some areas that many farmers I've talked to report their field drainage tiles are running."
The significance of this rainfall in August and in September is we're going to have a pretty good reserve of subsoil moisture going into the 2015 cropping season. "The wet 2014 growing season essentially guarantees it," says Taylor. "Especially as we move toward a likely El Nino condition in the months ahead. We've been moving slowly toward an El Nino since March, and people have kept asking—Where is it? Where is it? Where is the El Nino that's supposed to be developing? Well, last month was an El Nino month," says Taylor. "Even Phoenix, Arizona got some flooding."
He adds, "That's one of the first places in the 48 states that we really start to get the true symptoms indicating an El Nino is coming into place."
Signs are increasing for sustained El Nino to begin this fall
El Nino is the warming of the surface water in the Pacific Ocean near the equator off the coast of South America. The El Nino pattern develops every few years, alternating with La Nina, the cooling of the surface water. In years when an El Nino is occurring, it produces a rainfall pattern that is favorable for crop development and for good yields in the U.S. Corn Belt.
The latest report from the National Weather Service is predicting a sustained El Nino event that the weather service experts expect will begin sometime in September or October, and they believe it will be a weak El Nino. Does Taylor agree with that? "There's a 30% chance it will be weak," he says. "But there's around a 50% chance it will be moderate. And almost no chance it will be a strong El Nino, the way the indicators currently look."
But the strength of an El Nino—which means how warm the ocean water gets on the surface near the Equator—doesn't matter very much here in Iowa, says Taylor.
"If it's an El Nino that develops, we in Iowa tend to get milder winter weather and we tend to get a bit above normal chance of precipitation. In other places in the U.S., the strength of the El Nino makes a big difference in the weather they get. For example in Texas, or Ohio. But in Iowa, here in the middle of the U.S., I've noticed over the years that although El Ninos do vary one from another in terms of strength, the effect on our weather pattern isn't directly varying with that strength. In other words, if an El Nino develops, no matter how strong it is, we tend to have good growing weather in Iowa."
What's the winter weather outlook for Iowa?
If an El Nino develops as expected this fall, what will the winter be like? "Not as harsh as the past winter," says Taylor. "We'll probably hear someone say 'Ok, we've got a polar vortex effect, it is cold this winter. However, even in a normal winter we have three of those polar outbreaks. Last winter we had 9. Six make a harsh winter. So we had what I would call a harsh winter-and-a-half this past year—with 9 of those polar vortex outbreaks. This year the odds are that our winter may likely be more normal. Also, keep in mind that in some years we don't have any of the polar outbreaks or polar vortexes, as they are now being called."
Currently, as of mid-September, it looks like Iowa and a large part of the Corn Belt will likely have wet corn at harvest this fall—a lot of the corn crop is delayed a couple of weeks in maturity this year, thanks to the cooler than normal growing season.
So, if Iowa could have drier, warmer weather for harvest that would be good for the crop to help it dry down in the field for harvest. "If the weather turns dry in this next couple of weeks, which I think it will, and that pattern carries through harvest this fall, yes, that will be good," says Taylor.
Drier, warmer weather needed to dry down crops in fields
He adds, "If your corn is in good health, so that it is standing well in the field, it would probably be best to get your soybeans harvested first, as farmers usually do. Because beans don't stand well. They shatter and everything else. But it now looks like weather conditions for this fall will be good for the corn to dry down. The probability of field dry down of crops this fall is much better now than it was a couple weeks ago."
As of September 15, corn and soybeans are hastening toward maturity and that will give the crops more opportunity for field dry down—"if we get low humidity and days without rain and hopefully some sunshine," says Taylor. "Those factors contribute to dry down of crops in the field. Of course, all of the fields aren't at full maturity yet. So we need the killing frost to hold off at least until normal dates for various locations in Iowa."
For more information and an update on weather conditions, go to Iowa State Mesonet and Ag Weather facts.