A credible weather timeline is not simply a list of the largest values found near a property. It is a traceable sequence showing what was reported, when it was reported, where it was measured, and how each record relates to the event under review.
Begin with time discipline
Record the time exactly as it appears in the source, including the stated time zone, then normalize a working copy for comparison. This avoids a common problem: placing observations in the wrong sequence because one source uses UTC, another uses daylight time, and another uses local standard time.
This is not a theoretical concern. NOAA’s documentation for Local Climatological Data Version 2 states that its summary PDF forms use Local Standard Time and do not apply Daylight Saving Time. A timeline assembled without reading the product documentation can therefore be displaced by an hour during part of the year.
Keep the measurement label attached
Every value in the timeline should retain its identity. At minimum, record:
- the source and station or product;
- the original timestamp and time basis;
- the variable, units, and averaging or reporting interval;
- the station location and relevant site relationship;
- any missing, estimated, corrected, or quality-controlled status; and
- the retrieval date and a durable copy or citation.
A reported gust, a two-minute average, a daily maximum, and a modeled wind estimate are not interchangeable. Preserving the label prevents an observation from acquiring more precision—or a different meaning—as it moves into a chart or report.
Let gaps remain visible
A missing observation is not a zero, and it is not permission to interpolate without explanation. NOAA notes that station coverage and available variables vary, and that some records contain gaps. Those limitations belong in the timeline because they help define what the record can and cannot establish.
When multiple sources are available, comparison can be valuable. Agreement may strengthen the description of the event; disagreement may reveal timing, exposure, sensor, or product differences that require closer review. Either way, the purpose is not to select the most dramatic number. It is to understand the record.
Build an audit trail, not just a graphic
A clear chart is useful, but a reviewer should be able to trace each plotted point back to its source. Preserve the original records, station metadata, retrieval details, and any transformation used to produce the working timeline. If a time zone was converted or a unit changed, document it.
The result is more than a chronology. It is an evidence map that lets the professional assess relevance, identify uncertainty, and explain why a particular source was—or was not—relied upon.
Primary references: NOAA NCEI Local Climatological Data, LCDv2 documentation, and the National Weather Service ASOS User’s Guide.