Fowey Rocks Light · Photo: http://www.birdphotos.com · CC BY 3.0Key Biscayne’s winters are milder and less snowy than most of the U.S.
A typical July afternoon reaches 89°, a January night drops to 62°, and snow is almost unheard of.
A year in Key Biscayne at a glance
Each month’s typical high and low, and what it brings.
What stands out about Key Biscayne’s climate
Compared with towns across the U.S., with Key Biscayne’s place in Florida beside it.
What a year in Key Biscayne feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
Frost is rare
Frost and day counts come from NOAA’s station at Cape Florida, FL, 1.4 miles from the town’s center, at about the same height.
The 2023 USDA map puts Key Biscayne’s center in zone 11a: the coldest night of a typical winter, averaged over 1991–2020, reaches about 43°. Plant labels use the zone; frost dates tell you when to plant.
90° days by month
Average days at 90° or more
About 61 inches of rain a year
June is the wettest month and December the driest. Rain falls on about 127 days a year. Snow is rare: about 0.0" in a normal year at Cape Florida, FL, so most winters see none.
Rain + melted snow by month
Inches of water
Heating and cooling a home in Key Biscayne
2% of the work is heating, so air conditioning is the bigger bill. No month averages under 55°.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Cape Florida, FL.
Living with Key Biscayne’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
Zone 11a. Frost almost never comes, so tender plants can often stay out through winter.
Months with highs of 62–84° and lows of 40° or more: January, February, March, April, November and December. 1.1 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Key Biscayne from natural hazards, hurricanes are the largest share (52%); heat waves, cold waves, winter storms and ice storms together are 12%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Key Biscayne and similar climates
TownRatings has no climate map of the towns around Key Biscayne yet.
Climates most like Key Biscayne’s, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| Key Biscayne, FL | 62° | 89° | 61" | 0.0" |
| Heeia, HI | 66° | 84° | 51" | 0.0" |
| Galliano, LA | 46° | 90° | 63" | 0.0" |
| Galveston, TX | 48° | 89° | 52" | 0.1" |
| Gulf Shores, AL | 44° | 90° | 62" | 0.0" |
Temperatures and precipitation come from NOAA’s 5 km grid; snow and day counts from the stations named on this page.
Warmer than it used to be
The last 30 years in Key Biscayne averaged 2.0° warmer than the 1900s. The biggest change is in February (+2.7°).
A bigger shift than in 90% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods.
How Key Biscayne compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Key Biscayne’s place among Florida’s.
Key Biscayne weather by month
Highs, lows and precipitation from NOAA’s grid at Key Biscayne’s center; snow, wet days and snow on the ground from Cape Florida, FL. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 76° | 62° | 2.4" | 0.0" | 8 | 0 | 63° – 73° |
| February | 77° | 63° | 2.3" | 0.0" | 7 | 0 | 63° – 76° |
| March | 79° | 66° | 2.5" | 0.0" | 6 | 0 | 66° – 78° |
| April | 82° | 70° | 3.3" | 0.0" | 6 | 0 | 72° – 81° |
| May | 85° | 74° | 5.6" | 0.0" | 10 | 0 | 76° – 82° |
| June | 88° | 77° | 8.9" | 0.0" | 15 | 0 | 80° – 86° |
| July | 89° | 78° | 6.4" | 0.0" | 15 | 0 | 82° – 85° |
| August | 90° | 78° | 7.8" | 0.0" | 16 | 0 | 82° – 85° |
| September | 88° | 77° | 8.6" | 0.0" | 15 | 0 | 81° – 84° |
| October | 85° | 74° | 7.3" | 0.0" | 13 | 0 | 78° – 83° |
| November | 81° | 69° | 3.4" | 0.0" | 9 | 0 | 71° – 79° |
| December | 78° | 65° | 2.3" | 0.0" | 8 | 0 | 61° – 78° |
| Year | 83° | 71° | 60.6" | 0.0" | 127 | 0 |
How much a month can swing
A normal is an average. December swings the most: from 1991 to 2020 its average ranged from 61° to 78°. August is the most reliable, staying within 3°.
Where Key Biscayne’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Key Biscayne’s center.
- Snow: Cape Florida, FL (NOAA station in town).
- Frost, freezing nights, 90° and 100° days, heating and cooling: Cape Florida, FL, 1.4 miles from the town’s center, at about the same height; the nearest station that passes our checks for distance, height and agreement with the grid.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Key Biscayne’s climate
What is the weather like in Key Biscayne?
A typical July afternoon reaches 89°, a January night drops to 62°, and snow is almost unheard of. Milder January nights than all but 79 U.S. towns; hotter July afternoons than 74% of U.S. towns.
How cold does it get in Key Biscayne in winter?
January nights average 62°. A night at 32° or below comes in only some winters (0.0 a year on average). In the coldest January of the last 30 years the month averaged 63°.
How much snow does Key Biscayne get?
About 0.0 inches in a normal winter at Cape Florida, FL, so most winters see none.
How hot does it get in Key Biscayne?
July, with a typical high of 89° and a low of 78°. About 55 days a year reach 90° (Cape Florida, FL).
When is the first and last frost in Key Biscayne?
Most years have no frost at all: a 32° night comes in about 0% of winters at Cape Florida, FL, usually in December or January.
What growing zone is Key Biscayne in?
Zone 11a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 43°.
What is the best time of year to visit Key Biscayne?
By one simple rule (highs of 62–84° and lows of 40° or more), January, February, March, April, November and December. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Key Biscayne getting warmer?
Yes: 1991–2020 averaged 2.0° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 90% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Key Biscayne.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.