The lowest sea-level pressure in the Western Hemisphere, and the highest reliably-measured non-tornadic sustained winds, are recorded in Hurricane Patricia, which strikes Mexico hours later, killing at least 13 and causing over $280 million in damages.

Atmospheric pressure, also known as air pressure or barometric pressure, is the pressure within the atmosphere of Earth. The standard atmosphere is a unit of pressure defined as 101,325 Pa (1,013.25 hPa), which is equivalent to 1,013.25 millibars, 760 mm Hg, 29.9212 inches Hg, or 14.696 psi. The atm unit is roughly equivalent to the mean sea-level atmospheric pressure on Earth; that is, the Earth's atmospheric pressure at sea level is approximately 1 atm.

The Western Hemisphere is the half of the planet Earth that lies west of the Prime Meridian and east of the 180th meridian. The other half is called the Eastern Hemisphere. Geopolitically, the term Western Hemisphere is often used as a metonym for the Americas or the "New World", even though geographically the hemisphere also includes parts of other continents.

Hurricane Patricia was the most powerful tropical cyclone on record worldwide in terms of maximum sustained winds and the second-most intense on record worldwide in terms of pressure, with a minimum atmospheric pressure of 872 mbar, just behind Typhoon Tip's 870 mbar. Originating from a sprawling disturbance near the Gulf of Tehuantepec, south of Mexico, in mid-October 2015, Patricia was first classified a tropical depression on October 20. Initial development was slow, with only modest strengthening within the first day of its classification. The system later became a tropical storm and was named Patricia, the twenty-fourth named storm of the 2015 Pacific hurricane season. Exceptionally favorable environmental conditions fueled explosive intensification on October 22. A well-defined eye developed within an intense central dense overcast and Patricia grew from a tropical storm to a Category 5 hurricane in just 24 hours—a near-record pace. On October 23, the hurricane achieved its record peak intensity with maximum sustained winds of 215 mph (345 km/h). This made it the most intense tropical cyclone on record in the Western Hemisphere and the strongest globally in terms of one-minute maximum sustained winds, tied with Typhoon Nancy of 1961.