Florida Keys in September: Warm Water, Quiet Beaches, and Better Rates
- Debbie Kronebusch
- 58 minutes ago
- 7 min read
If you're searching for the best time to visit the Florida Keys, September deserves a real look. It's the quietest month of the year in Marathon, FL, with some of the warmest water left over from summer, noticeably lower rates, and a strong offshore bite as mahi mahi and tarpon fishing hit their stride. This guide walks through exactly what September looks like on the ground, from local events to what makes it a smart time to book Casa Feliz, so you can plan with real details instead of guesswork.
Which Month Matches You? A 60-Second Self-Check
Before diving into everything September offers, run through these three quick questions. If your answers line up with the highlighted options below, September is shaping up to be your month.
1. What matters most to you when planning the trip?
The quietest, most crowd-free version of the Keys all year ← September match
Peak-season energy and the busiest events calendar
Cooler, milder daytime temperatures
A packed festival calendar built around one big event
2. Who's coming with you?
A big multi-generational crew that needs room to spread out ← September match
Just the two of us, somewhere quiet and low-key
A group of anglers chasing tarpon or mahi mahi ← September match
Young kids who need shorter travel days and early bedtimes
3. What does your ideal day in the Keys look like?
Hours in the pool or on the water, with an easy dinner and nowhere to be after ← September match
Bundled up for cooler mornings and quiet porch time
Wall-to-wall festivals, tours, and things to do
A slow, unhurried pace with very few plans at all ← September match
If most of your answers matched, September may be just perfect for you.
If your answers pointed elsewhere, this is part of a full year-round series on the best time to visit the Florida Keys, so there's a month ahead built around exactly what you're looking for.
What September Weather Feels Like in the Florida Keys
September in the Florida Keys means warm days, some of the last truly summer-warm water of the year, and noticeably lighter crowds than any other month. Daytime temperatures sit in the upper 80s to low 90s, mornings are typically clear and bright, and afternoon showers roll through and clear out quickly, often leaving a fresh breeze behind. It's ideal weather for a day built around the water, whether that means the beach, the pool, or a boat.
Metric | September Average | Why It Matters |
Daytime high | Upper 80s–low 90s °F | Great beach and pool weather all day |
Overnight low | Mid-70s °F | Warm enough for evening pool and porch time |
Water temperature | 85–88 °F | Some of the last warm-water days before fall |
Sunshine pattern | Sunny mornings, brief afternoon showers | Mornings and evenings are usually clear and bright |
The real highlight: with summer travelers gone and the winter crowd not yet arrived, September is the one month where the Gulf and Atlantic waters around Marathon are still warm and swimmable, but the beaches, restaurants, and boats all have far more room to spare.
A Quieter, More Relaxed Version of the Keys
September has a slower, easier pace than any other month on the calendar. Restaurants are easiest to get into all year, charter boats have the most open availability, and the beaches feel closest to empty. For families who'd rather spend a vacation actually relaxing than navigating crowds and long waits, September is the clearest example of that trade-off working in their favor.
That easier pace pairs naturally with a longer, more flexible daily rhythm: slow mornings on the water, an easy lunch, an afternoon by the pool, and dinner without a long wait.
September Is Prime Time for Anglers, and Lobster Season Is Still Going Strong
Regular lobster season, which opened in early August, runs all the way through March, so September visitors still get the full run of fresh local lobster on restaurant menus and dive shop trips. Offshore, September is also when the mahi mahi bite starts picking back up for its fall run, and with far fewer boats on the water than during the summer rush, anglers get more room to work a school without competing for it.
Mid-September also brings the Herman Lucerne Memorial Tarpon Cup, a well-regarded fly-fishing tournament held out of Islamorada in honor of a longtime conservationist, with proceeds supporting the Guides Trust Foundation of the Florida Keys. It's a short drive from Marathon and a fun reason to time a trip around, even for guests who'd rather watch from the dock than fish themselves.
Sombrero Reef, a short boat ride from Marathon, remains one of the best snorkel spots in the Middle Keys, with coral formations, tropical fish, and the occasional sea turtle or nurse shark. September's thinner crowds make it an easy add-on for a family that wants one guided excursion during the stay without turning the whole trip into a dive vacation.
September Events Worth Building a Trip Around
Date | Event |
Early September | Labor Day weekend — the last busy weekend before the Keys go quiet for fall |
Ongoing through March | Regular lobster season continues, with lobster specials on menus across Marathon |
Mid-September | Herman Lucerne Memorial Tarpon Cup, a fly-fishing tournament out of Islamorada benefiting the Guides Trust Foundation |
September–October | Mahi mahi fall run picks up offshore, with noticeably fewer boats competing for fish |
Islamorada is roughly 30 minutes up the Overseas Highway from Marathon, which makes the Tarpon Cup an easy day trip rather than a separate destination to book around.
Is September the Best Time to Visit the Florida Keys for Your Family?
September is a great fit for families who want the quietest, least crowded version of the Keys all year, still paired with warm, swimmable water and an active offshore bite for anyone who fishes. It also suits families who prefer a slower, more laid-back trip, with more room on the beach, easier restaurant reservations, and shorter waits than any other month.
If that sounds like your family, September offers something no other month can match: the calendar's quietest version of the Keys, at one of its best prices, while the water is still warm enough to enjoy all day.
Lower Prices and Fewer Crowds: The Off-Season Case for September
September is generally considered one of the best-value months in the Florida Keys, and that shows up directly in rental and hotel pricing. Once Labor Day passes, crowds thin out more than at any other point in the year, which means shorter waits at restaurants, easier boat charter bookings, and quieter beaches.
For a multi-generational group booking a larger home, that value gap tends to be even more noticeable than it is for a single hotel room.
A Day Trip to Bahia Honda State Park
For families who want one bigger excursion during a September stay, Bahia Honda State Park is about 20 minutes from Marathon and consistently ranked among the best beaches in the country. With summer crowds gone, September is one of the easiest times of year to find parking and space on the sand. The park's shallow, calm water is well suited to swimming and snorkeling, and the old Bahia Honda Rail Bridge makes for an easy, scenic walk between beach sessions.
What to Pack for September
Reef-safe sunscreen, required in many protected snorkeling areas
A light, packable layer for the occasional afternoon shower
Bug spray for evenings near the mangroves
A reusable water bottle to stay refreshed on warm, sunny days
Water shoes for reef walking and rocky shoreline entry points
Why a Private Home Makes More Sense in September
A private home is simply built for the kind of long, water-filled days September invites. Casa Feliz Florida Keys, a private waterfront home in Marathon that sleeps up to 10 guests, gives a multi-generational group its own resort-style pool and private beach to enjoy together between excursions, rather than sharing a single hotel pool with the rest of the property. With the fall mahi run underway and lobster season still open, a full kitchen means the group can cook up a fresh catch together instead of everyone squeezing into a booked-solid restaurant.
Casa Feliz's concierge program can also help line up guided fishing trips, snorkeling excursions, and day-trip bookings, so the whole visit comes together easily.
→ Related: Florida Keys Vacation Rentals Top Tips
Frequently Asked Questions
Is September a good time to visit the Florida Keys?
Yes. September is the quietest month of the year in the Florida Keys, with warm, swimmable water, noticeably lower rates, and an active mahi mahi and tarpon bite offshore.
What is there to do in the Florida Keys in September?
September highlights include the Herman Lucerne Memorial Tarpon Cup out of Islamorada, the ongoing regular lobster season, the start of the fall mahi mahi run, and snorkeling trips to reefs like Sombrero Reef near Marathon. Warm water also makes it a great month for swimming, paddleboarding, and kayaking.
Are Florida Keys vacation rentals cheaper in September?
Generally yes. September is considered one of the best-value months in the Keys, and rental and hotel rates typically run lower than in winter, spring break, or summer.
What's the weather like in the Florida Keys in September?
Daytime temperatures typically reach the upper 80s to low 90s °F with warm evenings in the mid-70s, ideal for beach days and evening pool time. Mornings are usually clear and sunny, with brief afternoon showers that pass quickly.
Is fishing good in the Florida Keys in September?
Yes. September marks the start of the fall mahi mahi run, tarpon fishing remains active enough to support the Herman Lucerne Memorial Tarpon Cup in Islamorada, and fewer boats on the water make it easier to book a charter on short notice.
What is the Herman Lucerne Memorial Tarpon Cup?
The Herman Lucerne Memorial Tarpon Cup is an annual fly-fishing tournament held out of Islamorada in mid-September, honoring a longtime Keys conservationist, with proceeds supporting the Guides Trust Foundation of the Florida Keys.
A private pool, a private beach, and enough room for the whole family to spread out in the quiet of September, together. Book your stay now. |
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