Keystone in Fall
In fall (September, October and November), Keystone sees average daytime highs around 83°F and overnight lows near 66°F, with 8.1 in of rain over about 26 wet days across the season. It is the 2nd-warmest season and the 2nd-wettest season.
Over the season highs ease from about 89°F in early September to 75°F by late November. The sky is clear or mostly clear about 38% of the time across fall, and the air most often feels oppressive.
Fall is Keystone's 3rd-best season to visit on our travel score. For the whole year in context, see Keystone's year-round climate.
- Avg daytime high
- 83°F
- 2nd-warmest season
- Avg overnight low
- 66°F
- Rainfall
- 8.1 in
- 26 wet days
- Avg wind
- 7 mph
- Travel score
- 6.0
- 3rd-best season
- Months
- Sep · Oct · Nov
Temperature in Keystone in Fall
Over the season highs ease from about 89°F in early September to 75°F by late November.
A typical fall day in Keystone reaches about 83°F and drops to 66°F overnight. The warmest of the three months is September, the coolest November.
How fall really feels in Keystone
Once humidity and wind are folded in, fall brings about 33 days that feel above 90°F and 0 that feel at or below 32°F.
The story in fall is heat — humidity pushes the afternoon "feels like" well above the raw temperature.
Keystone weather by month
How the three fall months (September, October and November) compare with the rest of the year — the season's months are highlighted.
| Month | High / Low (°F) | Rainfall (inches) | Wet days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|
| Jan | 69° / 51° | 2.5 | 6.5 | 10.4 | 7.1 |
| Feb | 72° / 53° | 2.2 | 6.3 | 11 | 7.4 |
| Mar | 76° / 57° | 2.5 | 6.3 | 11.8 | 7.7 |
| Apr | 82° / 63° | 2.1 | 6 | 12.7 | 7.0 |
| May | 87° / 69° | 2.3 | 7.3 | 13.4 | 5.3 |
| Jun | 89° / 74° | 5.0 | 16.4 | 13.8 | 3.6 |
| Jul | 89° / 76° | 5.0 | 18.3 | 13.6 | 3.2 |
| Aug | 89° / 76° | 5.6 | 19.8 | 13 | 3.1 |
| Sep | 88° / 74° | 4.6 | 14.7 | 12.2 | 3.8 |
| Oct | 84° / 67° | 2.1 | 7.2 | 11.3 | 6.2 |
| Nov | 77° / 58° | 1.4 | 4.3 | 10.6 | 7.9 |
| Dec | 72° / 54° | 2.2 | 6 | 10.2 | 7.5 |
Cloud cover in Fall
The sky is clear or mostly clear about 38% of the time across fall.
Chance of precipitation in Fall
Keystone gets around 8.1 in of rain over 26 wet days across fall. The line is the day-by-day chance of measurable precipitation.
Humidity in Fall
Most of fall feels oppressive — the stacked bands show each day's mix of comfort levels, read off the dew point.
Wind in Fall
Winds average 7 mph across fall.
Sunrise & sunset in Fall
Daylight runs from about 12 h 36 min in early September to 10 h 24 min by late November. The lit band spans sunrise to sunset each day.
Solar energy in Fall
Average shortwave solar energy reaching the ground each day across fall, about 4.2 kWh/m².
Hazard calendar for Keystone
In fall, Keystone overlaps its atlantic hurricane and rainy season season. The full year is below, with each hazard's peak months called out.
Keystone sits in the Atlantic hurricane belt; the season peaks August–October.
Keystone's rainy season runs March–March, when most of the year's rain falls.
Is fall a good time to visit Keystone?
Our two travel scores rate fall for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal), averaged across the three months.
fall is a reasonable time to visit Keystone for sightseeing. The water and warmth also suit a beach or pool day.
What to pack for Keystone in Fall
From fall's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In fall, Keystone sees daytime highs around 83°F and nights near 66°F. Pack light clothes and rain gear. Worth having: sun protection. About 26 days see rain.
Sea temperature near Keystone in Fall
The nearest coast averages about 79°F across fall — the other half of the beach question. The full-year curve and swim-comfort zones are below.
The sea at the nearest coast (about 16 mi away) is warmest in August at about 86°F and coldest in February near 63°F.
It's comfortable for a long swim from Mar 21 to Dec 11 — about 8.7 months when the water holds above 68°F.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°F) | 64 | 63 | 67 | 73 | 78 | 83 | 85 | 86 | 84 | 80 | 73 | 67 |
| Comfort | Cool | Cool | Cool | Refreshing | Warm | Tropical | Tropical | Tropical | Tropical | Warm | Refreshing | Cool |
| Sea temperature (°F) | Comfort | |
|---|---|---|
| Jan | 64 | Cool |
| Feb | 63 | Cool |
| Mar | 67 | Cool |
| Apr | 73 | Refreshing |
| May | 78 | Warm |
| Jun | 83 | Tropical |
| Jul | 85 | Tropical |
| Aug | 86 | Tropical |
| Sep | 84 | Tropical |
| Oct | 80 | Warm |
| Nov | 73 | Refreshing |
| Dec | 67 | Cool |
UV index in Keystone in Fall
Clear-sky midday UV across fall averages around 7 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.
Under clear skies, the midday UV index in Keystone peaks around July 12 at about 11 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 19 at about 4 (moderate).
The index reaches 3 or more — the level where the WHO recommends sun protection — every month of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 5 | 7 | 8 | 9 | 9 | 11 | 11 | 10 | 9 | 7 | 5 | 4 |
| Level | Moderate | High | Very high | Very high | Very high | Extreme | Extreme | Very high | Very high | Very high | High | Moderate |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 5 | Moderate |
| Feb | 7 | High |
| Mar | 8 | Very high |
| Apr | 9 | Very high |
| May | 9 | Very high |
| Jun | 11 | Extreme |
| Jul | 11 | Extreme |
| Aug | 10 | Very high |
| Sep | 9 | Very high |
| Oct | 7 | Very high |
| Nov | 5 | High |
| Dec | 4 | Moderate |
Air quality in Keystone in Fall
Average fine-particle pollution (PM2.5) through the year — so you can see where fall falls, not just the annual average.
Air quality in Keystone is worst in July — around 18 µg/m³ PM2.5 (moderate), about 2.1× the cleanest month (November, 9 µg/m³).
Modeled monthly averages (CAMS reanalysis, 2015–2024).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 9 | 10 | 10 | 11 | 11 | 16 | 18 | 17 | 12 | 9 | 9 | 9 |
| Level | Good | Good | Good | Good | Good | Moderate | Moderate | Moderate | Moderate | Good | Good | Good |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 9 | Good |
| Feb | 10 | Good |
| Mar | 10 | Good |
| Apr | 11 | Good |
| May | 11 | Good |
| Jun | 16 | Moderate |
| Jul | 18 | Moderate |
| Aug | 17 | Moderate |
| Sep | 12 | Moderate |
| Oct | 9 | Good |
| Nov | 9 | Good |
| Dec | 9 | Good |
Where is Keystone?
Keystone sits at 28.2°N, 82.6°W, 39 ft above sea level, in United States. The nearest listed city is East Lake, 5.6 mi away.
Topography around Keystone
How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of Keystone.
Within 2 miles, the terrain around Keystone has only modest variations in elevation — a maximum elevation change of 98 ft around an average of 49 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 138 ft; within 50 miles, only modest variations in elevation — a maximum elevation change of 374 ft.
The land around Keystone is covered by trees (46%) and grassland (39%) within 2 miles, trees (56%) and artificial surfaces (20%) within 10 miles, and trees (39%) and water (37%) within 50 miles.
United States travel facts
- Power plugs
- Type A / B
- 120 V · 60 Hz
- Prices
- ≈ 100% of US
- price level, 2025
- GDP per capita
- $90,027
- 2025
- Happiness
- 6.8 / 10
- World Happiness, 2025
- Safe drinking water
- 98%
- of population, 2024
- Homicide rate
- 5.8
- per 100k, 2023
- Road deaths
- 12.7
- per 100k/yr, 2019
- Income group
- High
- World Bank
- Religion
Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.
Data sources
Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Keystone (28.1559°, -82.6212°, elevation 39 ft), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google.