The 2010 Atlantic hurricane season was an event in the annual tropical cyclone season in the north Atlantic Ocean. It was one of the most active Atlantic hurricane seasons since record keeping began in 1851 as 19 named storms formed. The season officially began on June 1, 2010, and ended on November 30, 2010, dates that conventionally delimit the period of each year when most tropical cyclones develop in the Atlantic basin. The first storm to form was Hurricane Alex, on June 25; and the last to dissipate was Hurricane Tomas, on November 7. Of the year's 19 named storms, 12 strengthened into hurricanes with five intensifying further into major hurricanes. The two most significant storms of the season, in terms of damage and loss of life, were hurricanes Igor and Tomas. Igor was one of the largest storms by gale diameter on record, and one that attained maximum sustained winds of 155 mph (250 km/h) before striking Newfoundland as a much weaker storm several days later. Tomas was a late-season tropical cyclone that rapidly intensified to reach maximum sustained winds of 100 mph (160 km/h) as it entered the eastern Caribbean Sea. Though the system did not make landfall, it severely affected the Greater Antilles, and impacted the southeastern Bahamas as a tropical storm before quickly moving into the open Atlantic. This timeline includes information that was not operationally released, meaning that data from post-storm reviews by the National Hurricane Center, such as a storm that was not operationally warned upon, has been included. This timeline documents tropical cyclone formations, strengthening, weakening, landfalls, extratropical transitions, and dissipations during the season. By convention, meteorologists use one time zone when issuing forecasts and making observations: Coordinated Universal Time (UTC), and also use the 24-hour clock (where 00:00 = midnight UTC). The National Hurricane Center uses both UTC and the time zone where the center of the tropical cyclone is currently located. The time zones utilized (east to west) prior to 2020 were: Atlantic, Eastern, and Central. In this timeline, all information is listed by UTC first with the respective regional time included in parentheses. Additionally, figures for maximum sustained winds and position estimates are rounded to the nearest 5 units (knots, miles, or kilometers), following the convention used in the National Hurricane Center's products. Direct wind observations are rounded to the nearest whole number. Atmospheric pressures are listed to the nearest