1. Identify the wind threshold, not the center crossing
These maps concern sustained winds reaching tropical-storm strength: at least 34 knots, about 39 mph or 63 km/h. A cyclone’s wind field extends away from its center, so those winds can begin before landfall. A predicted center-crossing time cannot replace the arrival-time product for another location.
2. Earliest reasonable arrival includes uncertainty
NHC defines this as a time before which there is no more than a 10% chance of the onset of sustained tropical-storm-force winds. It provides an earlier planning reference, not a guaranteed wind-free deadline. Do not interpret “earliest reasonable” as the earliest physically possible arrival, or postpone an earlier instruction from local authorities.
3. Most likely arrival describes the middle of timing
The most-likely graphic marks a time with equal likelihood of arrival before or after it. It does not promise that winds will start at that clock time. Nor does that timing statement by itself mean your location has a 50% chance of experiencing these winds; the separate wind-probability layer answers that question.
4. Combine timing with the probability of occurrence
NHC offers arrival maps over the cumulative wind-probability layer. Use the probability to understand whether the threshold may occur and the timing to understand when. Its product description limits timing information to locations with at least a 5% five-day chance. A blank timing area is not an all-clear for rain, surge, gusts or other hazards.
5. Keep the map’s own time zone
The time zone printed on the map can remain constant across the graphic even where the track crosses another zone. Read the date as well as the clock label, then convert once for your location. A phone’s display zone does not automatically change a downloaded image. Use the advisory issue time to identify which forecast cycle the map belongs to.
6. A fictional two-time example
Imagine an educational example with an earliest-reasonable label of Tuesday 8 AM EDT and a most-likely label of Tuesday 8 PM EDT for one town. The second value does not cancel the earlier one: it illustrates a spread of possible arrival times. This example is invented, has no storm or town forecast, and cannot set a preparation deadline. On a real map, read the accompanying probability and official instructions.
7. Compare the same product and forecast cycle
Compare earliest with earliest and most likely with most likely, using their issue times. NHC updates the arrival products with full advisory packages; this site’s refresh time is not the product’s issuance. A movement in a timing contour may reflect a new forecast, while switching map types can change the displayed time without any new forecast at all.
8. Choose the next source for the decision
For wind timing, open the current NHC arrival graphic; for whether a warning applies, read the named area in the latest advisory and the local warning product. Use separate rainfall and surge products for those hazards. Keep the source link when sharing, and follow local instructions that may require action before any arrival time shown here.
Official references
Reviewed 2026-10-13. Independent guide; follow NHC and local authorities for safety decisions.