The observation is the starting point.

One source, one station, one local day.

The sole weather source is the NOAA Aviation Weather Center data service, using METAR observations. This pilot never fills gaps with forecasts, modeled weather or another station. NOAA does not endorse YesterSky, and these recent observations are not certified records.

Each selected date starts at midnight in the station’s named time zone and ends at the following midnight. The first instant is included; the ending instant belongs to the next date. Daylight-saving changes can produce 23- or 25-hour days. Phoenix uses America/Phoenix and remains on 24-hour local days.

The date range is yesterday through 30 local days ago. A date remains selectable even if it is partial or unavailable. The oldest dates can have incomplete coverage when the service first begins retaining records.

Samples tell you what was reported.

Temperature lows and highs are the lowest and highest retained samples, not official daily minimum and maximum temperatures. Wind speed and decoded gusts are reported fields. “Highest decoded gust” excludes peak-wind remarks in raw reports, which can describe stronger winds. Those remarks remain visible without an unproved claim about their occurrence time or local day.

The timeline uses actual observation times. Coverage shows occupied elapsed-hour intervals and the largest time gap, including the day’s boundaries. An occupied interval does not prove continuous observation or that every field was present. Missing temperature, wind or precipitation values remain missing.

Source temperatures are in degrees Celsius, wind speeds in knots and decoded precipitation amounts in inches. The display converts these to the selected units without changing the source record.

Rain evidence is not a daily rain total.

Hourly, three-hour, six-hour and 24-hour precipitation fields remain separate. A missing hourly field does not mean all other periods are missing. Trace, unavailable sensors and missing amounts have different meanings; none is silently converted to zero.

Reporting periods may overlap or cross the selected day’s boundaries. YesterSky does not add them together, invent interval boundaries or turn a reported 24-hour amount into a local midnight-to-midnight total. The daily precipitation total is explicitly unavailable.

Where a raw report includes a recognized present-weather code, the tool can show it at that report’s observation time. That is evidence of a reported condition at an instant, not continuous rain between reports or a measured amount at your property. See the AWC METAR decoding guide. These reports cannot establish soil moisture or watering needs.

Duplicates, corrections and retained records.

Reports stay tied to their station and observation timestamp. Exact duplicates collapse. For competing reports at the same station and time, a corrected report takes precedence; later receipt orders otherwise equally ranked revisions. An unresolved equal-rank conflict is excluded and disclosed. Different observation timestamps are never merged.

A scheduled service refreshes a bounded set of recent records independently of your device. Older dates are revisited more slowly. Visitor lookups read retained snapshots rather than sending new weather-source requests. A shortened upstream response does not erase fuller retained coverage, while corrections are still reconciled.

The displayed retrieval time is the actual snapshot time, not the time you opened the page. A retained record may contain reports preserved from an earlier retrieval. Provisional status remains visible because upstream reports can change. If a refresh fails, the service may show an older retained snapshot with its true age; if that snapshot cannot be retrieved, it shows an unavailable response.

Distance and responsible use.

Distances use the verified station coordinates and the 2026 U.S. Census place reference points. They are straight-line reference distances, not distance from your device or address. Selected pilot stations are not necessarily the nearest stations.

Use YesterSky to understand the available recent observations. It does not replace certified records, safety alerts, a forecast or a site-specific measurement. To flag a source or calculation concern, send the result link to engineering@sparkandspoolco.com.