Americans just lived through one of the driest months in history. A big change is on the way

By Mary Gilbert, CNN Meteorologist

(CNN) — One of the driest months in United States history is coming to a close after causing the worst drought in more than 20 years in parts of the East as temperatures soar well above average there.

October could finish as one of the driest in the Lower 48 since the 1800s, according to data from the National Oceanic and Atmospheric Administration. As of October 25, the average precipitation across the Lower 48 was less than an inch. Only five months in the 129 years of records have ended with less than an inch of average precipitation over the Lower 48.

But an upcoming pattern flip could change things as the nation’s weather seesaws from one extreme to the next – a telltale sign of the increasing weather extremes as the planet warms due to fossil fuel pollution.

Hundreds of locales are experiencing one of the driest Octobers on record with dozens pacing for the driest, including some that haven’t received any measurable rain.

This October will likely end as the driest on record for New York City, Philadelphia and tied for the driest in Atlanta.

It could be the first month in Philadelphia dating to the 1800s without measurable precipitation. Only a few drops have fallen, not nearly enough to hit the 0.01-inch requirement to be considered measurable. Philadelphia hasn’t measured rain since late September and its 30-plus day dry stretch without it is the city’s longest such streak on record.

The same is true for Atlanta. The city typically gets a little over 3 inches of rain in October but hadn’t received a drop of rain until sporadic sprinkles tracked through the area Wednesday. Like Philadelphia, it still hasn’t received measurable rain.

A few places, particularly in the Central US, only had their dry streaks broken this week. New York recorded just 0.01 of an inch of rain on Tuesday, breaking a lengthy dry spell in a month when just over 4 inches typically falls.

Some places have swung from one extreme to the next.

Hurricane Helene ravaged the southern Appalachians with up to 30 inches of rain at the end of September and created catastrophic flooding that reshaped the region forever.

But the same area hasn’t recorded an inch of rain in October.

Florida is a notable exception to the intense dryness, but it came at the expense of another extreme: torrential, flooding rainfall from Hurricane Milton. Milton dumped so much rain in the Tampa area that parts of the region will have their wettest October on record. Tropical systems like Milton are getting more intense and unleashing heavier rainfall as the world warms.

Mounting consequences

Persistent high pressure dominating the eastern half of the US for much of October was a force field against wet weather and also caused temperatures in parts of the East and Midwest to feel more like summer than the peak of fall at times.

The combination of little-to-no rain and abnormally warm temperatures caused a flash drought to emerge in parts of the US and for drought conditions to dramatically worsen across the Lower 48.

Flash drought happens when drought conditions increase quickly, rather than over a multi-month or yearly timeframe, according to NOAA.

About 30% of the Lower 48 had at least moderate drought as October began. That figure is now 54% at the monitor’s latest update Thursday. Only about 11% of the country had moderate drought conditions or worse in early summer, so the increase over the fall and October alone has been astounding.

Just over 87% of the Lower 48 is at least abnormally dry – the most widespread this lowest level on the drought monitor has been in nearly two years.

The drought in a handful of states is the most significant in more than two decades.

More than half of New Jersey is experiencing severe drought after starting the month with none. It’s the state’s worst drought level since 2002. In nearby Delaware, nearly the entire state is in severe drought, also the worst since 2002. Severe drought is also happening in about 15% of Pennsylvania, the worst since 2002.

The expanding and worsening drought has serious implications for agriculture and transportation. Levels on the Mississippi River are so low that shipping loads must be constrained, the Associated Press reported Tuesday. The river is a critical transportation pipeline, especially for agricultural products, and this is at least the third year in a row it’s had water level issues.

Sixty percent of the water that flows into the lower Mississippi River comes from the Ohio River, where drought is rampant. Drought is also plaguing the upper portion of the Mississippi River.

Dry and abnormally warm conditions also ramped up wildfire danger in areas not typically associated with these kind of blazes in fall.

Multiple wildfires in Michigan, New Jersey and Massachusetts have burned at least 100 acres each in the past week alone, according to the National Interagency Fire Center.

November could be a turning point

November looks to be the start of a much wetter period for the US.

Outside of the West Coast, nearly the entire Lower 48 is likely to have wetter than normal conditions in early November, according to the Climate Prediction Center’s latest forecast.

For some parts of the East, a wetter November could start as soon as the month begins on Friday as a cold front swings through the region.

After that, a batch of widespread rain and storminess could develop in the central US over the weekend and persist into early next week, including on Election Day. Some of this wet weather could shift into the East around midweek.

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