Hurricane Stan in October was part of a broader weather system that killed 1,673 people and caused $3.96 billion in damage to eastern Mexico and Central America, with Guatemala hit the hardest.

Ahead of the formal start of the season, various groups issued forecasts for the number of named storms, hurricanes, and major hurricanes in the upcoming season, including Colorado State University (CSU), the Cuban Institute of Meteorology (InsMet), Tropical Storm Risk (TSR), and the United States National Oceanic and Atmospheric Administration (NOAA).

[5] By the end of July, seven tropical storms and two major hurricanes had developed within the basin, which prompted CSU, InsMet, NOAA and TSR to significantly increase their seasonal forecasts at the start of August.

The unusual activity was attributed to a persistent high pressure area over the Southeastern United States, the northeastward displacement and amplification of the Intertropical Convergence Zone (ITCZ) over the eastern Pacific, and above average sea surface temperatures in the Gulf of Mexico.

These factors reduced vertical wind shear and favored cyclonic flow, creating an environment highly supportive of tropical development.

[25] In addition, the El Niño–Southern Oscillation (ENSO) was in a neutral phase, lowering the likelihood of storms making landfall on the East Coast of the United States and leading to a concentration of impacts farther west.

[28] Lowered sea-level atmospheric pressures in the late spring and early summer of 2005 curtailed the strength of trade winds, resulting in a reduction of latent heat loss from the tropical Atlantic and Caribbean.

After five years of analysis, researchers were unable to confirm whether the recent increase in tropical cyclone activity could be attributed more to climate change than natural variability.

One potential hypothesis for these findings was a projected increase in vertical wind shear contradicted by warmer ocean temperatures for hurricanes to utilize.

[15] The hardest-hit area was the United States Gulf Coast from eastern Texas to Florida, affected to varying degrees by Arlene, Cindy, Dennis, Katrina, Ophelia, Rita, Tammy, and Wilma.

[69] The remnants of Arlene dropped approximately 6 to 7 in (150 to 180 mm) of rainfall in Warren County, New York, in just two hours, washing out several roadways and flooding numerous homes.

Continuing across the Caribbean Sea, Emily eventually strengthened into a Category 5 hurricane on July 16 to the southwest of Jamaica, reaching peak winds of 160 mph (260 km/h).

[41] While moving through the Lesser Antilles, the hurricane produced strong winds and heavy rainfall that caused flooding and landslides across several islands.

As it moved west into the Atlantic, it became more organized and the system developed into Tropical Depression Fourteen about midway between Cape Verde and the Lesser Antilles on September 1.

After moving away from the state, Ophelia weakened to tropical storm status for a fourth and final time due to stronger wind shear and dry air.

Ophelia killed three people – a drowning in Florida from high surf, a traffic fatality in North Carolina, and a death from a fall in Nova Scotia.

[122][126] Due in part to high temperatures preceding Rita's landfall and elderly susceptibility to excessive heat, at least 80 people died during the mass evacuation;[127] a coach fire en route to Dallas claimed 23 lives.

Impacts from heavy rainfall, gusty winds, and tornadoes associated with Rita affected much of the lower Mississippi River Valley, and over a million electricity customers lost power.

[132] Texas' Community Development Block Grant Disaster Recovery Program aided 1.85 million people in addition to supporting longer-term infrastructure repairs.

The newly formed cyclone exhibited deep convection in the southern semicircle,[134] but its cloud pattern quickly deteriorated under the influence of strong wind shear.

High pressure directed the cyclone toward the west-northwest, and the depression intensified into Tropical Storm Stan shortly before making landfall along the eastern coast of the Yucatan Peninsula.

In late September, an upper-level low formed west of the Canary Islands and moved westward, organizing into a subtropical depression early on October 4.

[150][151] An upper-level low over the southwestern Atlantic helped facilitate the formation of a large, monsoon-like gyre over the Caribbean Sea in middle October.

Wilma moved slowly through the warm waters of the western Caribbean Sea and began a period of rapid deepening on October 18 that lasted into the following day.

[61] The cyclone briefly attained tropical storm status, but wind shear prevented further development of the system, and advisories were discontinued on November 16 as it lost its closed circulation about 305 mi (490 km) southeast of Kingston, Jamaica.

[62][61] Delta originated from a broad and non-tropical low-pressure area that arose 1,380 miles (2,220 km) southwest of the Azores on November 19, initially moving northeast along the trailing fringes of a passing cold front.

Convection developed atop the center of the nascent disturbance two days later, and satellite data suggested that it was acquiring thermodynamic characteristics exhibited by tropical cyclones.

[67] El Dedo de Dios, a geological feature which had been pointing towards the sky for over a millennium and an important landmark for the Canary Islands, was toppled during the storm.

[167] Over the next couple of days, the system developed a low-level circulation and atmospheric convection increased as it moved north-westwards, before the NHC classified it as Tropical Storm Zeta during December 30.

[167] Over the next couple of days, the system gradually intensified further in a region of favorable anticyclonic outflow, as it slowly moved west-northwest in response to a mid-level low to the southwest.