When it rains in Penang it does not last all day. Maybe an hour. I could really stop right there but that won’t satisfy people who have been searching “monsoon season Penang”, or “when is the rainy season in Penang?”. Yes it rains more in October than January but it just doesn’t last that long. So maybe the rain is heavier in October for an hour and a bit lighter earlier in the year.
Occasionally you will get a nice big, loud storm that has a 20 minute peak and then drizzles for another hour then clears up.
On the heat side it is all relative. Very easy to read “its hot and humid year round.” Perhaps one should say “its never cold in Penang….”. If I was coming from a Middle Eastern Summer of near 50 degrees Celsius and landed during a Penang heatwave of 34 degrees I might need a sweater. The sun is different here though insofar as it “burns” more. Think a Southern Australian or Californian type heat so most people will burn at 30 degrees nicely. This plus humidity and yes it can get uncomfortable walking around Georgetown or anywhere in the full sun.
Our advice is try and do the walking around or exposed stuff in the morning or late afternoon / evening. Most places that most people will go or visit are built up so if you are caught in a downpour and don’t have an umbrella, shelter is not far away. If you are unlucky and get positively drenched at least you wont get cold here. Ever.