A weak tropical disturbance was first reported by the Air France and Iberia airlines east of the Lesser Antilles early on September 21.
Although it was speculated that the disturbance originated from a tropical wave near Cape Verde, the Weather Bureau considered the system too weak to be detected due to a lack of reports from the islands.
At 1800 UTC on September 21, while it was located 350 miles (560 km) east-southeast of Martinique, the disturbance became sufficiently organized for the Weather Bureau to classify it as Tropical Storm Janet, the tenth named storm of the season.
Upon classification, Janet quickly intensified as it moved to the west.
On September 22, Janet attained hurricane strength, and proceeded to intensify rapidly as it moved westward across the Windward Islands.
By 1200 UTC that day, Janet already attained Category 3 hurricane strength with maximum sustained winds of 120 mph (190 km/h), before stalling in intensification.

Shortly after 1700 UTC on September 22, the eye of Janet passed south of Barbados as a Category 1 Hurricane.
A reconnaissance flight into the hurricane discovered that the Hurricane Janet's eye measured only 20 miles (32 km) in diameter, with gale-force winds extending 120 miles (190 km) away from the center of circulation.
The flight also reported a minimum barometric pressure of 979 mbar (28.9 inHg).
After passing between the islands of Grenada and Carriacou in the morning hours of September 23, Janet entered an area of unfavorable conditions in the eastern Caribbean Sea.
As a result, the hurricane became disorganized, with winds weakening to 90 mph (140 km/h) by 1200 UTC on September 23.
A U.S. Navy reconnaissance plane entered the hurricane early on September 24, reporting a lack of organization, and noting an indiscernible center of circulation with weak rainbands.
However, the hurricane began to reintensify in favorable conditions, regaining major hurricane strength by 1200 UTC on September 24 and subsequently Category 4 hurricane intensity by the next day.

While trekking across the central Caribbean Sea, Janet was only slightly larger than while it was moving over the Windward Islands, with gale-force winds extending 125 miles (201 km) out from the center by September 25.
Remaining a Category 4 hurricane as it moved erratically westward across the Caribbean, a reconnaissance flight mission during the night of September 25–26 indicated strong rainbands with frequent lightning strikes and a well-defined eye, evidence that the storm was once again rapidly intensifying.
As it neared the Yucatán Peninsula on September 26, Janet began accelerating in forward speed.
After the reconnaissance flight Snowcloud Five was lost while making a penetration into the hurricane's eye, another flight early on September 27 reported a minimum pressure of 938 mbar (27.7 inHg), with winds in excess of 115 mph (185 km/h) "by a large and incalculable amount."
The hurricane was estimated to have intensified to Category 5 hurricane intensity—the highest rating on the modern-day Saffir–Simpson hurricane scale—at 1200 UTC on September 27, while in the western Caribbean Sea.
Janet continued to intensify afterwards, eventually reaching its peak intensity with maximum sustained winds of 175 mph (282 km/h), with gale-force winds having expanded to at least 250 miles (400 km) away from the center of the hurricane.
Janet maintained peak intensity as it passed over the Swan Islands before making landfall in extreme southern Quintana Roo, Mexico, just east of Chetumal, Mexico.
In that city, a barometer indicated a minimum barometric pressure of 914 mbar (27.0 inHg) in the eye of Janet.
At the time, this was the second-lowest pressure ever recorded on land in a landfalling Atlantic hurricane, behind the 1935 Labor Day hurricane, though Janet was later surpassed by hurricanes Dean and Gilbert, which also made landfall on the Yucatán Peninsula as Category 5 hurricanes.

Once over land, Janet considerably weakened to a Category 2 hurricane with winds of 105 mph (169 km/h).
After crossing the Yucatán Peninsula with a
A weak tropical disturbance was first reported by the Air France and Iberia airlines east of the Lesser Antilles early on September 21. Although it was speculated that the disturbance originated from a tropical wave near Cape Verde, the Weather Bureau considered the system too weak to be detected due to a lack of reports from the islands. At 1800 UTC on September 21, while it was located 350 miles (560 km) east-southeast of Martinique, the disturbance became sufficiently organized for the Weather Bureau to classify it as Tropical Storm Janet, the tenth named storm of the season. Upon classification, Janet quickly intensified as it moved to the west. On September 22, Janet attained hurricane strength, and proceeded to intensify rapidly as it moved westward across the Windward Islands. By 1200 UTC that day, Janet already attained Category 3 hurricane strength with maximum sustained winds of 120 mph (190 km/h), before stalling in intensification.
Shortly after 1700 UTC on September 22, the eye of Janet passed south of Barbados as a Category 1 Hurricane. A reconnaissance flight into the hurricane discovered that the Hurricane Janet's eye measured only 20 miles (32 km) in diameter, with gale-force winds extending 120 miles (190 km) away from the center of circulation. The flight also reported a minimum barometric pressure of 979 mbar (28.9 inHg). After passing between the islands of Grenada and Carriacou in the morning hours of September 23, Janet entered an area of unfavorable conditions in the eastern Caribbean Sea. As a result, the hurricane became disorganized, with winds weakening to 90 mph (140 km/h) by 1200 UTC on September 23. A U.S. Navy reconnaissance plane entered the hurricane early on September 24, reporting a lack of organization, and noting an indiscernible center of circulation with weak rainbands. However, the hurricane began to reintensify in favorable conditions, regaining major hurricane strength by 1200 UTC on September 24 and subsequently Category 4 hurricane intensity by the next day.
While trekking across the central Caribbean Sea, Janet was only slightly larger than while it was moving over the Windward Islands, with gale-force winds extending 125 miles (201 km) out from the center by September 25. Remaining a Category 4 hurricane as it moved erratically westward across the Caribbean, a reconnaissance flight mission during the night of September 25–26 indicated strong rainbands with frequent lightning strikes and a well-defined eye, evidence that the storm was once again rapidly intensifying. As it neared the Yucatán Peninsula on September 26, Janet began accelerating in forward speed. After the reconnaissance flight Snowcloud Five was lost while making a penetration into the hurricane's eye, another flight early on September 27 reported a minimum pressure of 938 mbar (27.7 inHg), with winds in excess of 115 mph (185 km/h) "by a large and incalculable amount." The hurricane was estimated to have intensified to Category 5 hurricane intensity—the highest rating on the modern-day Saffir–Simpson hurricane scale—at 1200 UTC on September 27, while in the western Caribbean Sea. Janet continued to intensify afterwards, eventually reaching its peak intensity with maximum sustained winds of 175 mph (282 km/h), with gale-force winds having expanded to at least 250 miles (400 km) away from the center of the hurricane. Janet maintained peak intensity as it passed over the Swan Islands before making landfall in extreme southern Quintana Roo, Mexico, just east of Chetumal, Mexico. In that city, a barometer indicated a minimum barometric pressure of 914 mbar (27.0 inHg) in the eye of Janet. At the time, this was the second-lowest pressure ever recorded on land in a landfalling Atlantic hurricane, behind the 1935 Labor Day hurricane, though Janet was later surpassed by hurricanes Dean and Gilbert, which also made landfall on the Yucatán Peninsula as Category 5 hurricanes.
Once over land, Janet considerably weakened to a Category 2 hurricane with winds of 105 mph (169 km/h). After crossing the Yucatán Peninsula with a 
Hurricane Janet