Weather radar

Islamorada weather radar

The last 50 minutes of NEXRAD over the Keys, animated, with the warnings in force and how to read a Keys storm. Not for navigation.

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Latest
5 dBZ
Mist, very light rain
20 dBZ
Light rain
30 dBZ
Moderate rain
40 dBZ
Heavy rain
50 dBZ
Very heavy rain, small hail
60 dBZ
Hail, severe storm core

Key Largo to Marathon with the reef and the near backcountry. Frames are about 5 minutes apart; the newest is usually 2 to 6 minutes behind real time, and the mosaic refreshes every 5 minutes while this page is open. Radar: NWS NEXRAD mosaic via Iowa Environmental Mesonet. Base map: Esri, GEBCO, NOAA, Garmin, HERE and other contributors.

Reading the radar in the Keys

Summer storms build inland

From May to October the sea breeze builds cumulus over the Everglades and the mainland by early afternoon. Which way the storms drift depends on the steering wind: on a south-west or west flow they come across Florida Bay to the Keys and the reef; on the usual easterlies most stay over the peninsula. On light-wind mornings the storms can form over the Keys and the Bay themselves. Watch the 50-minute loop for the direction of travel, not just where the colour is now.

Fronts come from the north-west

From November to April a cold front shows as a line of showers coming down the peninsula, sometimes with a squall line ahead of it. The rain is the small part: the wind swings north behind the front and the oceanside builds over a few hours. The line on the radar is your clock for getting back to the ramp or the dock.

The radar sees rain, not wind

A dry gust front or a waterspout shows little or nothing. The Keys lead the country for waterspouts, which form under lines of growing cumulus on humid, light-wind mornings: look at the sky as much as the screen. The beam from Key West and Miami is several thousand feet up by the time it reaches Islamorada, so low showers can look weaker than they are.

Reading the colours

Greens are light rain you can fish through; yellow is a steady soaking; orange and red are heavy rain with gusty wind and lightning likely; purple and white are hail and severe cores. A cell that grows and brightens on each frame is building; one that fades and spreads is collapsing, and a collapsing storm often sends out its strongest gust.

Lightning and squalls

On a charter the captain watches this for you and makes the call: a trip cut short for weather is seamanship, not bad luck, and most captains will try to make the time up or reschedule. Ask on the dock how they handle afternoon storms in summer.

The conditions page carries the NWS marine forecast and the small-craft advisories; the map shows the ramps, marinas and bridges to run for.

National Weather Service radar loops

The NWS's own loops from the two radars that cover Islamorada, and the regional mosaic. They are the fallback if the viewer above cannot load, and the place to look during tropical weather.

Radar questions

How current is the radar on this page?
The mosaic is the National Weather Service NEXRAD composite, published as map tiles by the Iowa Environmental Mesonet and refreshed about every five minutes; the newest frame is usually two to six minutes behind real time. The page re-fetches it every five minutes while it is open.
Why is the radar blank?
A blank map means no rain within the radars' reach, which in the Keys is most winter days. If the tiles fail to load, the National Weather Service loops below and radar.weather.gov are the backup.
Can I rely on this radar on the water?
Use it as one input, with the NWS marine forecast, the sky and your own judgement. Phone signal fades a few miles offshore and the radar cannot see wind, waterspouts or a dry gust front. Leave early rather than late, and never use this page or any map on this site for navigation.
How far away should lightning be before I leave?
The standard rule is to be off the water, or under hard cover, before lightning is within 10 miles: if thunder follows the flash in under 30 seconds, it is closer than that. Wait 30 minutes after the last thunder before going back out.

Sources and more

Let the captain read the sky

A charter means someone who has watched ten thousand Keys afternoons decides when to run and when to wait. Book a day on the water with A Fishing Guru.

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