Audit recorded weather observations

Start with a traceable record

This activity uses real NOAA National Weather Service API observations preserved in weather-observations-v1. The three deliberately selected records are KJFK, New York Kennedy International Airport; KDEN, Denver International Airport; and KSEA, Seattle-Tacoma International Airport. They are not synthetic weather cases, a random sample or a complete station network.

The lesson reads the frozen local snapshot, not a live feed. Each record retains its official query URL, source fields and retrieval timestamp. The NWS provides observations through its public API, whose documentation describes the service as open data. NWS API documentation.

Create a paper ledger with columns for station identifier, observation timestamp, retrieval timestamp, temperature and unit. Copy a value together with its metadata instead of carrying an unlabeled number into a comparison.

Keep observation and retrieval times separate

All three observations are dated 2026-10-25 in UTC. KJFK is timestamped 19:05, KDEN 19:30 and KSEA 19:10. They were retrieved later, around 19:58:30–31 UTC, with separate exact retrieval timestamps preserved for each record. Retrieval time tells you when the snapshot acquired the record, not when the station observed the weather.

With KJFK as A and KSEA as B, the signed observation-time difference A minus B is −5 minutes. Reverse the pair and the difference becomes +5 minutes. Comparing KDEN with KJFK gives +25 minutes. The sign describes the order of observations; it does not indicate a weather delay or a travel time between stations.

The timestamp suffix +00:00 identifies UTC. Comparing local clock times from different zones without converting them can create a false chronology. This lesson keeps one time basis throughout.

Convert units without changing the observation

The temperature and dew-point fields use degrees Celsius. Wind speed uses kilometers per hour. To convert wind speed to meters per second, divide by 3.6, because 1 km/h = 1000 m/3600 s.

KJFK’s reported wind speed is 14.832 km/h, which converts to 4.12 m/s. KDEN and KSEA each report 9.252 km/h, or 2.57 m/s. This conversion changes the representation, not the measured wind. Additional decimal places in a converted value do not establish additional instrument accuracy.

Write one conversion as a chain of units on paper, then reverse it to recover the source value. Separately record the qualityControl code supplied for that field. The browser preserves those raw codes; it does not transform them into a new quality grade or infer that a retained value is exact.

Do not fill gaps with plausible-looking information

The rawMessage field is an empty string in each saved record. The lesson cannot reconstruct a formal raw METAR message merely because the station is an airport. Preserve the missing message rather than inventing a coded report from selected fields.

Other entries explicitly use null, including all three precipitationLast3Hours values. A missing amount is not zero. A unit code beside a null value identifies the intended quantity but does not supply a measurement. Keep the distinction visible in your ledger.

The exact source records are KJFK at 19:05 UTC, KDEN at 19:30 UTC and KSEA at 19:10 UTC. A live service may not retain an old observation indefinitely; the versioned snapshot preserves the inputs used here.

Describe a comparison precisely

The stored temperatures are 18, 13 and 11°C respectively. KJFK minus KSEA is therefore +7°C for these two observations. This is a comparison between specified records, not a simultaneous spatial map, an all-day temperature difference or a statement about typical climate.

Transfer: separate time and unit errors

A hypothetical record observed at 12:00 UTC is retrieved at 12:20 UTC and reports wind speed 18 km/h. What time should label the observation, and what is its speed in m/s?

Check the weather-observations transfer

The observation time is 12:00 UTC; 12:20 UTC is the retrieval time. The wind speed is 18/3.6 = 5 m/s. Neither conversion nor download time changes what the original observation represents.