Weather in Key West in May

A good month. May is a solid month to be in Key West. Highs average 27.1 °C, lows 26.1 °C, and rain falls on 14 days — nothing in the month is working against you.

May ranks 7 of 12 in Key West: past the worst of the year but short of January, which is the month to book if the dates are open.

This is persistent light rain rather than storms: 14 wet days but only 2 heavy ones. It rarely cancels anything outright, and it rarely fully clears either. A jacket beats an umbrella. Nothing specialised needed — this is the month you pack for the trip rather than for the weather.

What the averages hide

Averages flatten a month, and this one hides a few things: it never really gets hot: not one day in an average May reaches 30 °C; the day barely swings — 0.9 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest May day reached 29.1 °C and the coldest night fell to 22.7 °C, and the wettest single day dropped 106 mm — roughly 110% of the month's rain in one day.

This is the volatile part. May rainfall has ranged from 12 mm to 377 mm across the twenty years measured — a 365 mm spread around an average of 96 mm. The average is real but almost no individual May looks like it, so treat the figure as the middle of a wide range rather than a forecast.

Wind sits around 16.7 km/h — a steady breeze rather than a nuisance, and welcome on the warmer days, and humidity runs at 76%, high enough to notice on the warm days without dominating them.

How May sits in the year

The month is on the way up: 1.6 °C warmer than April, and June adds another 1.7 °C. Late in the month feels noticeably different from the start of it, which is worth knowing if the trip is short. Rain is the thing that moves: June brings 8 days more of it, so the earlier half of a flexible trip is the safer half.

Daylight in May

May is at or near the longest days of Key West's year: 13.3 hours of daylight, gaining 0.5 hours across the month. Evenings are the real gain — dinner outdoors still happens in full light.

Sea temperature

The sea sits at about 27.2 °C in May — warm enough that the water offers no relief from the heat. The sea peaks at 29.9 °C in August and bottoms out at 24.9 °C — water lags the air by a month or two, which is why the best swimming often comes after the best weather.

How busy it gets

Shoulder. The value months — prices ease off and you get the place closer to itself.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

May in Key West versus nearby

If Key West is one option among several, the nearby comparison is worth making. Miami is close enough to be a coin toss — within a degree on temperature, 2 days more rain. Cape Coral is the weaker option in May — 3.1 °C warmer, 1 day more rain.

So: May works, with January the better month by 17 points if the dates can move. If they cannot, nothing here should stop you booking.

Every month in Key West

See all twelve months in Key West, or where else to go in May.