El Nino Watch
Charts can load only a date range, or a lighter version of long series (one average per day, or every Nth point).
Data and trust
Options when a chart loads a series: "since" and "until" dates, and "downsample": `daily` (one average value per day) or a number N (keep every Nth point; the most recent point is always kept). The series list can be filtered by source, source category (ocean index, maritime, local, ...) or name.
Limits. Do not read extremes from a downsampled chart; load the full range for that. A daily average of a series that has one value per day is the value itself.
A daily average smooths hourly buoy data: peaks within a day are flattened. Every-Nth keeps real measured values but skips the ones in between.
Some series are large (hourly buoy temperatures, 40 years of weekly SST). Lighter charts load faster, especially on a phone on island internet.