A tense situation is unfolding in Tulsa, Oklahoma, where officials are hoping that 70-year-old levees will withstand an unprecedented, prolonged test to keep back the swollen Arkansas River, which has risen to an all-time record high after weeks of heavy rain.

Why it matters: The flooding that has gripped the nation's heartland will eventually affect the price of food, as farmers cope with fields that have turned into lakes at a time of year when staple crops such as corn and wheat should be planted already. In addition, the damage from the floods, which started in the Upper Midwest earlier this year and now stretch all the way down the Mississippi River, likely exceeds $1 billion in individual states alone, with a far higher aggregate cost.

Details: Massive thunderstorms have dumped torrential rains in Oklahoma, Kansas and surrounding states during the past two weeks, sending the Arkansas River in western Arkansas and eastern Oklahoma to its highest level on record.

In Fort Smith, Arkansas, on Tuesday morning, the river rose to 2 feet above its previous all-time high. The forecast crest is not predicted to occur until Wednesday evening, after the river rises another 2 feet.

All-time record crests are predicted from Fort Smith southward to near Little Rock.

In Tulsa, additional rain on Tuesday could force officials to release more water from the Keystone Dam or risk water levels overtopping the floodgates, which could be catastrophic, the Tulsa World reports.

Tulsa's levees are being tested in ways that may become more common with global warming, as heavy rains and floods increase in frequency.

"This is the culmination of a flood that is now in its fourth week," David Williams, with the U.S. Army Corps of Engineers in Tulsa, told the newspaper.

In Oklahoma, flooding cut off all roadways into the town of Braggs in Muskogee County Tuesday — turning the town into an island, the New York Times noted.

The impact: Floodwaters are slowly making their way down the Mississippi River toward Louisiana, rattling nerves and setting records.

Officials announced Monday they will open the Morganza Spillway in Louisiana for only the third time since it was built in 1954. The river is expected to crest there by June 2 at the second-highest level on record.

"The current flood fight is historic and unprecedented," the Corps said in a statement, noting that this year's Mississippi River floods are likely to become the longest such event on record, beating a 1973 flood that lasted 225 days.

The background: "In the Southern Plains, Oklahoma has far and away been the poster child for this event," Victor Murphy of the National Weather Service tells Axios. "By the time May 31st rolls around, we fully expect May of 2019 to surpass October 1941 as the 2nd wettest month on record for Oklahoma, behind only May 2015."

According to Murphy, many counties along and north of I-44 from Oklahoma to the Missouri border have seen at least 16 to 19 inches of rain for the month, with more to come. "These 30 day values are on the order of 1-in-50-year to 1-in-100-year events," he says.

Between the lines: The ongoing flooding is consistent with scientific studies showing the increasingly apparent effects of human-caused climate change. A warmer atmosphere holds more water vapor on average, which contributes to an uptick in heavy precipitation events. Such trends have been seen in much of the U.S. in recent decades.

In addition, other research shows ties between persistent, highly amplified weather patterns such as this one and long-term climate change.

Go deeper: