What is in the historical record?
The primary evidence consists of the original ALERTBAY/PCBFLAGS archive plus new Safe2Swim observations collected automatically. Those records are never overwritten.
To extend the timeline, Safe2Swim also recovers explicit Bay beach-flag reports from National Weather Service Tallahassee Surf Zone Forecast products archived by the Iowa Environmental Mesonet. A recovered record is promoted only when no primary observation exists for that date, and every recovered row keeps its source-product identifier and URL.
How was the recovered history validated?
The recovered NWS record was compared directly against primary observations on more than six hundred overlapping dates. Agreement was above 98% for both the latest and peak daily base flag and above 99% when comparing whether at least one reported flag matched. That makes the recovered series useful secondary evidence while still keeping the primary archive authoritative.
Purple dangerous-marine-life overlays are handled more conservatively: explicit recovered Purple reports are retained, but an older NWS record that does not mention Purple is treated as Purple-unknown rather than proof that no Purple flag was flying.
What patterns can history reveal?
Persistence
Elevated beach hazards often occur in episodes rather than isolated moments. Safe2Swim tracks how frequently red-or-worse days are followed by another elevated day.
Intraday changes
Primary alert records can contain multiple updates in one day. Safe2Swim preserves those changes separately from recovered daily NWS reports so alert timing is not overstated.
Seasonal context
Multiple years of observations allow vacation planners to compare similar calendar windows with a substantially larger evidence base.
Environmental associations
Weather, wind, waves, swell and tide features are joined to finalized flag records to study which combinations are associated with elevated flags.
Why Safe2Swim keeps evidence tiers separate
The raw observation table answers “what was reported, when, and by which source?” The daily summary answers “what happened on this date?” The modeling table answers a different question: “which finalized environmental features can be compared statistically with the flag outcome?” Keeping primary and recovered provenance visible makes the extended record auditable instead of silently blending sources.
Download the data
Safe2Swim publishes the unified history as well as the recovered NWS tier so the source decisions can be inspected independently.
Download observation CSV Download daily CSV Download recovered tier
Use the archive for planning
The Vacation Planner translates historical observations into a tourist-friendly comparison for future travel windows while keeping sample size, source tier, and limitations visible.