Unseasonable Warmth Bakes Plains States as Dry Conditions Raise Early Fire Concerns

Although most of the country is having cool and wet weather, the Midwest is going through a remarkable period of temperatures above the normal level and precipitation below the normal amount, causing some officials to be keeping an eye out for early-season fire weather conditions.

Throughout September the temperatures in the central Plains and the Upper Midwest have been 10 to 15 degrees higher than average and this trend is not expected to stop as we move into October. This week cities such as Omaha, Des Moines, and Minneapolis have had several days when the temperature reached the 80s, some of the places even approaching 90°F—temperatures which are more usual for August than for early fall.

The updated temperature forecast from NOAA indicates that above-average temperatures are expected over almost all areas west of the Continental Divide, such as the northern and central Plains and the Upper Mississippi Valley. This warmth is due to a steady high-pressure ridge remaining over the Rockies, which is pushing the cold fronts northwards and keeping the jet stream well to the north of that area.

Though the warm weather has been a welcome thing for farmers who are rushing to complete the harvest and for people who are taking advantage of the longer outdoor season, the absence of rain is now causing concern. In many places throughout the western Plains and the Upper Midwest the amount of precipitation received in the last 30 days has been less than 25 per cent of what is normal, and in some areas there has been no measurable rainfall since early September.

Soil moisture is decreasing quickly and a number of rivers and streams are dropping below the levels which are normal for this time of year. Although drought conditions have not yet been reached, the situation is worrying, particularly if the dry trend continues into late October and November.

Because of the warm temperatures, the low humidity and the gusty winds, the fire weather conditions have been only marginal for several days this week, especially in Kansas, Nebraska and the Dakotas. The National Interagency Fire Center has raised the fire danger ratings for parts of the central Plains and is warning that sparks from farm machinery or from burning outdoors could easily start grass fires.

“The conditions are now ideal for a rapid spread of fire,” Sarah Mitchell, an analyst with the NIFC, said. “The relative humidity is dropping down into the teens and 20s and there are sustained winds of 20 to 30 mph. Therefore, any ignition source could cause a grass fire to move quickly.”

The good news for people who are hoping for some relief is that the models indicate a change in pattern during the third week of October, the high-pressure ridge being expected to break up and making it possible for colder and more active weather to move into the area. This may provide the much-needed precipitation to the dry regions, although it will also mean the end of the long period of warm weather.

At this stage, people should make sure they are drinking enough fluids, reduce physical activity when the heat is at its highest, and avoid doing anything that could cause a fire. As the harvesting continues, farmers should keep an eye on the moisture content in the soil and the condition of the crops.