Firstly, here we are not discussing the weather, though I will use weather related examples.
This is examining the other WHETHER.
WHETHER vs. IF is important to remember because the meaning of a sentence can sometimes be different depending on your use of WHETHER or IF.
The formal rule is to use IF when you have a conditional sentence and WHETHER when you are showing that two alternatives are possible.
1. The meaning of IF
Let’s start with the meaning of IF. IF is a conjunction introducing a conditional clause or, in other words, IF starts a sentence that presents a condition; I will go for a walk, IF the rain stops. The condition of going for a walk is the rain stopping.
2. The meaning of WHETHER
The meaning of WHETHER is more focused. WHETHER indicates an indirect question involving stated or implied alternatives. It might be expressing a doubt or choice between alternatives.
I will go for a walk, WHETHER it rains or not;
I don’t know WHETHER I’m invited.
Notice in the second example the alternative is implied, you are either invited or not invited, and there are no other choices.
Sometimes the words are interchangeable. The meaning of the sentence will not change; for example,
I don’t know IF he went for a walk in the rain, and
I don’t know WHETHER he went for a walk in the rain.
Both mean the same thing—we don’t know about the walking in the rain.
4. Conditional or Options
Now, we can see how the choice of word can change the meaning of a sentence.
I don’t know IF he went for a walk in the rain or the snow.
In this sentence we not only do not know if he walked in the rain or the snow but we don’t know if he even went for a walk.
I don’t know WHETHER he went for a walk in the rain or the snow.
Here, we know he went for a walk, we just do not know if it was raining or snowing.
5. When to use WHETHER OR NOT
In the use of WHETHER OR NOT the OR NOT can often be superfluous to the sentence; for example, I don’t know WHETHER OR NOT I am invited. The OR NOT does not change the meaning or add emphasis, so we do not need it.
You need the OR NOT if you are doing it regardless of WHETHER.
I am going for a walk regardless of WHETHER it is raining or snowing.
I am going for a walk WHETHER OR NOT it is raining or snowing.
As for Tyson; IF I punch you with my left or right hand, implies he might not hit you; WHETHER I punch you with my left or right hand, means he is going to hit you!