Seasonality and extreme weather events are key aspects of past, present and future climate systems. Few climate archives preserve long enough continuous time series in sufficiently high temporal resolution to analyse (sub-)seasonal aspects of past climates. (Sub)tropical marine giant clams (Tridacna) are fast growing (mm-cm/year) and long lived (up to 100 years) organisms which build large aragonitic shells (up to 1m). Therefore, their shells are ideally suited to evaluate seasonality and extreme weather events in (sub-)tropical reefs, ever since their emergence in the early Miocene. Here we present a Miocene multiproxy palaeoenvironmental record from the Indo-Pacific region, specifically the Makassar Strait (East Borneo), spanning over 50 years. The temporal resolution of the oxygen and carbon isotope record is sub-monthly to seasonal, while it is sub-daily for elemental ratios (X/Ca; X=B, Na, Mg, Sr, Ba). The internal age model was determined using Daydacna, our recently developed Python script that uses wavelet transformation of measured daily elemental cycles to quantify growth rates within the shell (Arndt et al. 2023; G-cubed). This established a 57 years long growth duration. The seasonal patterns of the proxies measured in the fossil clam suggest that the Miocene reef was affected by precipitation and discharge dominated seasonality, affecting the availability of light and nutrients throughout the year. Extreme peaks in elemental ratios occurring together with structural changes in the shell could indicate extreme weather events.