Best Time to Visit Key West: Month-by-Month Highs, Rain, Sea Temperature and the Quiet Season

KEY WEST · THE 12-MONTH VERDICT · 24.5° N

Key West sits closer to Havana than to Miami, and the year barely moves. The coldest month averages a high of 75.8°F in January; the hottest averages 90.6°F in August. That is a swing of under fifteen degrees across twelve months, and the sea never drops below 76.3°F.

So temperature is not what decides your dates. Rain does, and the storm calendar does. September collects 7.24 inches of rain across 10.2 wet days; March collects 1.53 inches across 2.9. Same island, same latitude, two completely different weeks off work.

On this page

• Best month to visit Key WestMarch, with the numbers behind it
• Key West water temperature by monthSea normals, and the 80°F line from May to November
• Month-by-month highs, lows and rainfallThe twelve-month table
• Worst month to visit Key WestSeptember, 7.24 inches and 10.2 wet days
• Quiet season in Key WestAfter Labor Day to mid-November, plus early December
• Is April or November better in Key WestThe shoulder compared, degree by degree

Two facts carry most of the decision. The dry half of the year runs December through April, five months that each stay under 2.2 inches of rain. The Atlantic hurricane season runs June 1 to November 30, with most activity between mid-August and mid-October. Florida’s wider seasonal pattern lives in our state calendar, and the 113-mile drive down is in the road-trip guide.

Key West weather month by month: highs, lows, rain and sea

The year splits cleanly in two. From December to April the island is warm and dry, with rain under 2.2 inches a month and three or fewer wet days. From May to October it is hotter, muggier and far wetter, cresting in September at 7.24 inches over 10.2 days. Nothing here is ever cold: even February keeps days at 77.4°F.

Two months do the switching. May flips the dry side over: rain climbs from April’s 2.07 inches to 3.12, wet days from 2.8 to 4.1, and the sea jumps 4.8 degrees to 84.6°F. November flips it back, cutting October’s 5.67 inches to 2.05 and its 7.6 wet days to 3.0 while the water still holds 81.2°F.

September is the hardest month, and it is hardest for a specific traveler: the one with fixed dates. Beyond the 7.24 inches, an average September records 1.9 days with an inch of rain or more, roughly five times April’s 0.7 heavy-rain days measured the same way. Anyone able to travel on short notice, or willing to book refundable, sees a different September entirely.

One caveat about the source. Every figure here for air temperature and rain comes from NOAA’s 1991-2020 normals at station USW00012836, the gauge at Key West International Airport on the island’s south side, not from a hotel pool deck or a reef mooring. The wet-day counts use the American threshold of 0.10 inch. Sea values come from a separate marine dataset offshore, averaged over 2015-2024.

When is the best time to visit Key West?

March. Days average 79.6°F with nights at 69.3°F, rain totals 1.53 inches over 2.9 wet days, the water sits at 78.6°F, and on the 15th you get 12 hours 3 minutes of daylight with sunset at 7:37 p.m. local time. It also falls three months clear of the hurricane season on either side. No other month puts that combination on the table.

Its neighbors both lose on a specific number. April runs 3.0 degrees warmer by day but adds 0.54 inch of rain and nearly doubles the heavy-rain days, 0.7 against 0.4. February is marginally drier by count, 2.4 wet days, and pays for it with air 2.2 degrees cooler and water 2.3 degrees cooler at 76.3°F. If you swim, March wins the trade.

March also suits the trips that need cooperative water. The boat crossing to Dry Tortugas and any reef morning depend on light wind more than on air temperature, and the dry half of the year is when both behave. Pair it with the state’s dry season in the Florida calendar, or with an Everglades day on the way down, when wildlife concentrates at the same time of year.

When can you swim in Key West? Sea temperature month by month

Take 80°F as the line where nobody hesitates on the ladder. Seven months clear it: May at 84.6°F, June 86.6, July 88.7, August 88.8, September 88.3, October 84.2 and November 81.2. Five sit below, and only just. April misses by 0.2 degrees at 79.8°F, March reads 78.6, December 77.6, January 76.5, and the annual floor is February at 76.3°F. That floor is still bath-warm by most American standards.

Read those numbers as what they are: an average of daily maxima over 2015-2024, not a 24-hour mean. The water peaks in the afternoon, so a 7 a.m. snorkel starts below the printed figure, and the value describes open water offshore rather than any one beach. Between February and April the gap matters most, because half a degree decides how long you last.

When is Key West quietest?

The quiet stretch is a calendar fact, not a price claim. It opens after Labor Day, when the school year has taken families off the road, and it runs to about mid-November. A second, shorter lull sits in the first ten days of December, before the holiday weeks fill the island. Both fall wholly or partly inside the hurricane season, June 1 to November 30, and that is exactly why they are quiet.

What you gain is space and warm water at once. October keeps highs of 85.8°F and a sea at 84.2°F, warmer than anything March can offer, with 11 hours 37 minutes of daylight on the 15th and sunset at 7:01 p.m. By mid-November the water still reads 81.2°F while rain has already fallen to 2.05 inches. Sunset crowds thin, restaurant tables open up, and the sandbars belong to fewer boats.

What you lose is dry days and certainty. October averages 5.67 inches of rain over 7.6 wet days, including 1.5 days with an inch or more, and September is worse on every one of those counts. Booking inside the season means accepting cancellation risk on rooms, flights and boat charters alike. November 15 also gives you only 10 hours 59 minutes of daylight, with the sun gone at 5:41 p.m.

Which month should you avoid in Key West?

September, if your dates cannot move. It is the wettest month by a wide margin at 7.24 inches, more than four and a half times March’s 1.53, and it averages 10.2 days with measurable rain out of thirty. It also holds September 10, the statistical peak of the Atlantic hurricane season, inside a stretch from mid-August to mid-October when most activity happens. A one-week window with a non-refundable room is the worst way to meet it.

For a diver, September reads differently. The water averages 88.3°F, its second-warmest reading of the year, highs hold at 89.0°F, daylight still runs 12 hours 19 minutes on the 15th with sunset at 7:31 p.m., and the town is at its emptiest. Book refundable, keep the schedule loose, and treat the rain as an afternoon event rather than a lost day.

Is the shoulder season worth it in Key West?

The two shoulder months are April and November. April runs 3.0 degrees warmer by day than March at 82.6°F, on 2.07 inches of rain. November is warmer still than the winter peak, 81.0°F against January’s 75.8°F, on 2.05 inches. Both stay inside the dry half’s rain budget, and both sit one step away from a month you would think twice about.

The shoulder’s real prize is the sea. November water at 81.2°F runs 2.6 degrees above March and 4.7 above January, the difference between a quick dip and a long afternoon in the shallows. April at 79.8°F beats February by 3.5 degrees. Add daylight: April 15 gives 12 hours 47 minutes, nearly two hours more than January 15’s 10 hours 49.

The subtractions are small but real. April doubles March’s heavy-rain days, 0.7 against 0.4, and adds half an inch of total rain. November’s 3.0 wet days and 2.05 inches beat February’s 2.4 days and 1.54, and its 10 hours 59 minutes of daylight is 1 hour 48 short of April’s. November also stays inside the storm season until the 30th.

Our verdict: take April without hesitation, and take November with a refundable booking. The month to weigh carefully is May, where the sea reaches a glorious 84.6°F but rain climbs to 3.12 inches over 4.1 days and June 1 waits at the far end. If a half-inch of rain matters less to you than three degrees of water, the shoulder is the better trip.

The last word

Pick March if you get to choose, April if the calendar chooses for you, and November if warm water outranks a dry forecast. Then budget for one line nobody quotes on the booking page: Monroe County levies a 5.0% transient rental tax on top of the 6% state sales tax, so every room night arrives 11% heavier than the rate you agreed to. Spend the difference on an early boat, before the wind fills in and the reef stops being glass.

Sources & data for this guide

• Monthly normals for highs, lows, precipitation and wet-day counts at 0.10 inch · NOAA NCEI 1991-2020, station USW00012836 (Key West International Airport) · checked Sep 10, 2026
• Sea surface temperature, mean of daily maxima 2015-2024 · Open-Meteo Marine API · checked Sep 10, 2026
• Daylight length, sunrise and sunset on the 15th of each month, converted to America/New_York · sunrise-sunset.org · checked Sep 10, 2026
• Hurricane season dates, the September 10 peak and the mid-August to mid-October window · NOAA National Hurricane Center · checked Sep 10, 2026
• Monroe County 5.0% transient rental tax, filed with the 6% state sales tax · Florida Department of Revenue form DR-15TDT · checked Sep 10, 2026
• Editorial admission: we hold no price series for Key West lodging, so the quiet season here is described by the calendar (school year, storm season, holiday weeks) and never ranked by cost. Rates, taxes and boat schedules change · confirm with operators when you book.