I have a Filipino friend that always tells me that it's cold and she has to wear a jacket, but when I check the weather, it's 24°c. I mean I only wear t-shirts at this temperature! Is there something different there that make you feel cold? I need to know if I need more clothes on my trip to the Philippines.
No. It is about the personal degree of comfort. If you wear a T-shirt at 24C, then that's what you need. Just be sure to check the lows too in the region where you are going but the Philippines are quite hot in general, so people from there are feel colder than others at the same temperature.
Funny thing is that I did visit the Philippines and noticed that even the locals were suffering from the heat and humidity in early fall. I had suffered heat the entire month before in Indonesia, so it seemed like a relief but never did I feel cold given that I live in Canada.
Last year I observed the same in Brazil. I went during Canadian summer landing in Brazilian winter. It was still 27C or so in Rio, so I was hot but I see many people wearing jackets at that temperature and when going inland to Petropolis which dipped to 22C about, they had jackets and hats!
It's all relative! That's why in Canada I feel cold when it does down to 0C in October but then it goes up to 0C in May, it feels warm!
Depending on your personal physiology and where you are coming from, maybe, maybe not. Take one along in checked baggage at least.
It's all about personal acclimatization. Military personnel have to do it all the time. If you are coming from about the 45th parallel, maybe Michigan in the US, or the UK, or Scandinavia, especially in the fall, winter or early spring, then 24°C will seem warm to you, perhaps even hot. No jacket would be necessary.
On the other hand, if you are coming from below the 45th parallel, or somewhere in the warmer climes, during the summer, or even an equatorial locale anytime, then that same temperature will seem cool, or worse.
The first thing you need to ask yourself is, are you "thin-skinned" or "thin-blooded"? Do you need a light sweater around the house when your flat-mates are all in t-shirts? or are you the one who is sweating while others shiver?
The next, even more important thing to consider is how long you will be there. Please realize, no matter where you are coming from, or what general body type or metabolism you have, if you are staying in the Philippines for many days or a few weeks, then sometime during that time you will acclimatize with that weather. You won't notice the humidity as much, and whatever the average temperature is, that will become "normal".
Now you have to return home. I come from Northern Michigan, in the US. I went to Phoenix, Arizona for my honeymoon for three weeks years ago. We left in September. Packed (and wore) light shirts and cotton pants. Had lots of T-shirts and shorts, etc. Perfect for the area and weather. Returned home in early October, and almost had frostbite by the time we got home from the airport. That was a memorable trip (for more reasons than that, but still.)
You are asking whether or not to pack and/or wear a light coat or jacket. Take it. Pack it in your carry on. If you need it, it's there, if not, oh well.
The Philippines have mountains too and in the evening they certainly get chilly. A popular example of this is Baguio, a city 1,400 meters above sea level both of Manila. Wikipedia reports an average low in December of 13°c, which might not be comfortable with shorts in the humid evening.
Most of the country however rarely drops below 20°c, which is a little cold for a local but an European might very well endure.