PAGASA rainfall warnings tell you how hard it will rain across a whole province. They cannot tell you what that rain does at your address. Here is what yellow, orange, and red actually mean in millimeters, why two houses on the same street can flood differently under the same warning, and how to pair a live weather warning with a permanent hazard profile of your lot.
A rainfall warning tells you how hard it is about to rain. It does not tell you what that rain will do at your address. Those are two different questions, and the color on your phone screen only answers the first one.
PAGASA issues rainfall warnings in three colors. Each color is tied to a measured amount of rain in one hour, not to how frightening the sky looks.
Here is a way to picture 30 millimeters in an hour. Imagine a flat baking tray left outside. In sixty minutes it fills to three centimeters deep. Now imagine that happening across an entire city at once. On a hillside, that water runs downhill and is gone. On flat ground with a canal that is already full, it has nowhere to go, so it rises.
That last sentence is the whole point. The same 30 millimeters produces a completely different day depending on the ground it lands on.
Rainfall warnings are issued for areas, not addresses. PAGASA might raise orange over a whole province, or over Metro Manila as a block. That is the right way to warn millions of people quickly, but it means the warning cannot tell you whether your street floods.
Two houses four hundred meters apart can have opposite outcomes under the exact same orange warning. What separates them is not the weather. It is the ground:
None of those four things change when the storm passes. They are properties of the location, not of the week.
A weather warning is temporary information. A hazard profile is permanent information. They answer different questions, and you need both.
The sky question is: how much water is arriving, and when? PAGASA answers this, in real time, for free. Follow the official bulletins and follow them closely during a storm.
The ground question is: what happens to water once it arrives here? That answer does not change between storms. It is set by elevation, slope, drainage, distance to waterways, and which modeled hazard zone the lot falls in. You can find it out on a calm, dry Tuesday, which is a much better time to learn it than at eleven at night in the rain.
Most people only ever ask the sky question. That is why the same neighborhoods appear in the news every single season.
Once you know your ground answer, the colors stop being generic and start being personal. A yellow warning means something different to someone on a mapped high flood zone at four meters elevation than it does to someone on a plateau at thirty.
Here is a practical checklist:
A hazard screening is exactly that, a screening. It is built from national government datasets, so it reads the landscape, not your particular lot. It does not know that the developer next door raised their lot by a meter last year and pushed the runoff onto yours. It does not know that a canal is clogged, that a pump station is broken, or that a new wall changed where water goes. It also cannot forecast the weather; PAGASA does that, and their bulletins remain the authority during an actual storm.
What a screening does well is remove the guesswork from the part that never changes. It turns "I think we are okay here" into a set of numbers you can check, argue with, and show to someone else. For a property decision, that is usually the missing piece, because the ground answer is the one nobody volunteers and most people never think to ask for.
CheckHazard does not replace a professional geotechnical or engineering survey.