improve rain charts

internal/db/series.go

@@ -74,7 +74,7 @@ func (d *DB) ObservationSeries(ctx context.Context, site, bucket string, start,
 				max(light_lux) AS light_lux_max,
 				avg(battery_mv) AS battery_mv_avg,
 				avg(supercap_v) AS supercap_v_avg,
-				avg(rain_mm) AS rain_mm_avg,
+				max(rain_mm) AS rain_mm_avg,
 				max(rain_start) AS rain_start_max
 			FROM observations_ws90
 			WHERE site = $1