Weather Quiz

 

Homestead Farm, Poolesville, Maryland

True or False.

The first half of October has produced both accumulating snowfall and near triple-digit heat in the nation’s capital over the last 45 years.

Feeling like fall

 

Feeling like fall, Bethesda, Maryland

After DC’s warmest first week of October since 2013, it’s felt more like late-October the last few days.  While high temperatures in the nation’s capital reached the low to mid 80s through October 6, they’ve been below average ever since.

Washingtonians interested in cooler weather should be happy that a symbolic date has arrived in the nation’s capital.  October 11 is the latest in the calendar year that it’s been 90° or hotter in Washington, D.C.  This date’s record high was set in 1919 when it reached 90°. 

The length of daylight and the angle of sunlight both decrease throughout October, so it stands to reason that average highs also decrease during the month.  By Halloween, the average high temperature in the nation’s capital is only 64 degrees.  That’s down from an average high of 75° on October 1.

However, those who are not ready for the chill of late autumn can find summer-like warmth on occasion during the first half of October.  As recently as 2019, DC residents experienced the hottest October temperature on record when it was 98° on October 2.  The nation’s capital has averaged one 90-degree October day roughly every three to four years over the last 30 years according to the National Weather Service.

October can feature a variety of weather in the Mid-Atlantic Region, from the remnants of Hurricane Opal in 1995, to the severe weather of October 2011 when weak tornadoes touched down in Virginia, to the summer-like heat of 2007 when 90-degree heat occurred on three consecutive days.  Winter-like weather can even occur in October.  For example, on October 29, 2011, the high temperature at National Airport was only 42 degrees (more characteristic of mid-January), and a trace of snow fell. 

No 90-degree heat has occurred in the nation’s capital in more than a month, since it was 93° on September 8.  Now that the symbolic date of October 11 has arrived, those looking forward to cooler weather can expect no more 90-degree heat in the Mid-Atlantic Region until next year.  Moreover, 80-degree warmth becomes less and less likely with every passing October day. 

NOAA’s Climate Prediction Center expects the coolest weather of the fall season to arrive in the nation’s capital early next week with highs only in the 50s.

Major October hurricanes in the Gulf of Mexico

 

Hurricane Opal making landfall, October 1995 (Source: NOAA)

Although the tropical Atlantic gradually begins to quiet down after its September peak, the Gulf of Mexico remains a favored area of development until the end of the season.  Warm ocean water (at least 80° Fahrenheit to a depth of at least 200 feet) is required for a tropical storm or hurricane to intensify under ideal atmospheric conditions. Some of the warmest water anywhere in the Atlantic Basin can be found in the Gulf of Mexico.

Smaller areas of water that features higher sea surface temperatures can sometimes influence hurricane intensity.  The Gulf of Mexico’s Loop Current is a smaller area of warmer ocean water than can influence tropical systems.  There is also something known as a “warm core ring,” which is simply an eddy or localized current of water that breaks off from the main ocean current (like the Gulf Stream or Loop Current) and can linger over an area of a few to a few hundred kilometers.  These warmer waters can provide additional fuel for an intensifying hurricane.  Here are some examples.

Zeta (2020):  Zeta reached peak intensity on October 28 as a major Category 3 hurricane as it made landfall in Louisiana.  Its highest sustained winds were 115 mph with a minimum central air pressure of 970 millibars (mb).  Although Zeta quickly weakened after its landfall, it remains noteworthy for being the latest in the season a major hurricane made landfall in the contiguous United States.  Zeta caused $5.1 billion in U.S. damages (2023 dollars), according to NOAA, along with five fatalities.

Michael (2018):  Hurricane Michael became only the fourth Category 5 hurricane to make landfall in the United States and first since Hurricane Andrew in 1992.  It also remains one of the few hurricanes that intensified up until its landfall.  Michael reached peak intensity as it made landfall along the Florida panhandle with sustained winds of 160 mph and a minimum central air pressure of 919 millibars (mb).  That part of Florida had seen several Category 3 hurricanes, but never a Category 4 or 5 storm.  Michael caused $30.2 billion in U.S. damages (2023 dollars) and claimed 16 lives during the storm, according to NOAA.

Lili (2002): Hurricane Lili reached peak intensity on October 2 while over the Gulf of Mexico as a Category 4 storm with sustained winds of 145 mph.  Lili weakened precipitously before its landfall in Louisiana as a Category 1 hurricane.  Hurricane Lili caused $1.26 billion in damages (2023 dollars) and two fatalities in the United States, according to NOAA.

Opal (1995):  Opal was one of five major hurricanes to form during the very active 1995 season.  It was also the strongest hurricane of the season as a Category 4 with peak winds of 150 mph and a minimum central air pressure of 916 millibars.  Fortunately, it weakened to Category 3 intensity before making landfall near Pensacola, Florida on October 4.  The DC Metro Area saw severe weather from the remnants of Opal on October 5.  Opal caused $9.3 billion in U.S. damages (NOAA) and 27 hurricane-related deaths according to the CDC.