Nothing seasonal is running in Kuala Lumpur & the west coast in September — which is its own answer. Pack for the temperature.
Going in July
The driest usable stretch of the middle of the year. Still humid, still the occasional storm — just fewer of them.
What this means for your bag
Real sun protection
High-factor sunscreen, a hat with a brim and sunglasses. Reef-safe sunscreen is worth buying before you go — it is expensive and hard to find at the beach.
See the Beach & Pool Kit packRoom for humidity
Everything stays slightly damp. Pack fewer clothes and plan to wash them, and keep anything that must stay dry in a sealed bag.
See the Summer Sun Kit packA bottle you will actually refill
Heat like this needs far more water than you think. A filter bottle also spares you buying a plastic bottle every two hours.
See the Health & Wellness pack
Build a packing plan around the season you are actually travelling in.