United States - weather in October

October is the second autumn month in the United States.
Temperatures are already quite high in the interior of the north, in the Great Plains (see Fargo), in the Great Lakes area (see Chicago) and in New England (see Portland in Maine), where frosts may occur, especially in the second half of the month. In the Rocky Mountains (see Helena, Denver) it can even snow.
However, in the center-north there can be an unseasonal warm period, with summer-like weather, called Indian summer.
In the center-south, on the other hand, temperatures are mild, and in the extreme south, both in the deserts of the south-west (see Phoenix) and in Florida (see Miami) it is still hot.
However, the temperature can drop sharply when cold air masses move southward.
In the month of October, starting from the north, after the first cold (but not freezing) nights, the trees take on autumn colors (fall foliage), which are often more intense and spectacular than in Europe. Generally, the peak is recorded at the beginning of the month in the north, in the middle of the month in the north-central, around the 41st parallel, and from mid-October to early November in the center-south.
Precipitation is already frequent and abundant in the western part of the Pacific Northwest, in the states of Washington and Oregon (see Seattle), and also in the north-east, in New England (see Boston, Portland in Maine). Instead, in central-southern California (see San Francisco, Los Angeles), the rains are still rare, as well as in the deserts of the south-west (see Las Vegas, Phoenix).
In the east-central part of the United States, east of the arid areas, the rains are still quite abundant in the central-southern part, influenced by the Gulf of Mexico, also due to thunderstorms.
From June to November is the season of hurricanes, which can affect the states bordering the Gulf of Mexico (Texas, Louisiana, Mississippi, Alabama and Florida) and the southernmost states of the Atlantic (Georgia, North and South Carolina). Occasionally, hurricanes can move northward and affect the other Atlantic coastal states as well.
More rarely, a hurricane from the Pacific to the west of Mexico, usually weakened, can affect the southwest (southern California, Arizona, New Mexico). In October, we are at the end of the period when hurricanes are most likely.

The sea is warm enough for swimming in the Gulf of Mexico, in Florida and in the Atlantic coast states up to North Carolina.
Instead, to the west, on the Pacific Ocean, the sea is cold even in California.


See also: United States, the weather in September - November
The climate of United States