H U R R I C A N E S E A S O N
In the Eastern Pacific, hurricanes begin forming by mid-May, while in the Atlantic, Caribbean and Gulf of Mexico, hurricane development starts in June. For the United States, the peak hurricane threat exists from mid-August to late October although the official hurricane season extends through November. Over other parts of the world, such as the western Pacific, hurricanes can occur year-round. (From NOAA's Climate Prediction Center.)
Hurricane researcher Chris Landsea (NOAA/OAR/AOML) has been collecting a great variety of quotes about the massive storms he studies, and one of them is an old Florida fishermen's saying which summarizes the science in rhyme:
"June--too soon. July--stand by. August--look out you must. September--remember. October--all over."
(from The Everglades: River of Grass Marjory Stoneman Douglas, 1890-1998)
We now know what makes for an active, or inactive, hurricane season in terms of SST (sea surface temperatures) and variations in the Atlantic jet streams. As these two NWS graphics show, the presence of Highs or Lows in the mid-Atlantic changes the direction of the upper winds, and promotes or reduces the likelihood of hurricanes. (See also WHAT and WHY for more on hurricanes.)
(images provided by NOAA and the Climate Prediction Center)