September 26, 2024 Climate Outlook

September 26, 2024 3:20 PM

Key Points

  • Hurricane Helene expected to make landfall Thursday evening
  • Above average temperatures expected for the next few weeks
  • Crop condition is mostly good to excellent across the state

Past Weather

In the past 30 days, much of the state has received 25-70% of average precipitation, with the exception of southern Iowa, which had 70-130% of normal precipitation, most of which fell within the last 14 days.  Dryness during August and September has led to the expansion of D0 (abnormal dryness) across most of the state and some areas of D1 (moderate drought) creeping into northeast Iowa.Precipitation deficits in Iowa in the past 30 days.

Average temperatures across Iowa for the past 30 days have been around 3 to 5 degrees warmer than normal. The average daily high temperature in September is generally 75 degrees, and the average daily low temperature is about 55 degrees. Now that we are into September, daily average temperatures will decline more rapidly. Since September 1st, daily high temperatures have dropped around 5-10 degrees.

Crop Update

This week’s NASS crop progress shows that corn conditions are 77% good to excellent, up 27% compared to last year. Soybean conditions are 78% good to excellent, up 31% compared to last year. Subsoil moisture is 54% adequate, which is 34% higher than this same time last year. Soils are starting to dry, but we expect fall to be drier than spring.

Climate Outlook

The Weather Prediction Center quantitative precipitation forecast shows no rain expected across the state for the next 7 days. Hurricane Helene, however, will bring significant rainfall to the southeastern United States.

Climate Prediction Center outlooks show warm and dry conditions are expected for the next several weeks. The 6-10 outlook (valid October 2-6) shows average temperatures leaning above average for most of the central and eastern parts of the state and likely above temperatures in the western region of Iowa. There is a 50-60% chance of below-average rainfall in the eastern half of the state and a 60-70% chance of below-average rainfall in the western half of the state.  The 8–14-day outlook (valid October 4-10) shows temperatures likely above average and precipitation leaning below average.

Above average temperatures expected across much of the U.S. in the next two weeks. Below average precipitation expected for most of the U.S. in the next two weeks.

The 3–4-week outlook shows a warm and dry signal to start October. The one-month outlook for October, issued September 19, shows equal chances for below, above, or normal temperatures and precipitation leaning slightly below normal. The seasonal outlook shows equal chances above, below or average for both precipitation and temperature.

La Niña has a 71% chance of developing from September to November. Once La Niña has developed, it is expected to persist into winter, January through March of next year.  This La Niña event is projected to be weak.