This gets many high school students ready for the real world. Having a tardy policy shows that if we are constantly late, there will be consequences such as detention or doing a job that the teacher of the class that you are always late to assigns to you. The way many see this is a curse this is a very easy way to keep yourself on time. You work on your time management skills. Though life and weather may change the time that you get there but that shows that you must try to plan ahead of the bad weather or talk to your teachers of what's going to make you late. Being late doesn't help anyone, but being on time teaches us many lessons to live by.
There are many factors that are out of students control that can make them late such as weather, injury, or keeping in mind that students are still children and cannot yet drive having parents that wake up too late and living far enough from the school that walking there would not get you there on time. It is unfair for students to be punished for factors outside of their control. Students may also be late because they were up late studying and overslept or redoing/reprinting their homework if it was destroyed. It does not make sense that a student would be punished for trying to do good in school even if it causes them to be a little late.
I know life happens as does you car breaking down, or the many other reasons the high school students are late. Where I go to school the weather is a big problem with dirt roads and icy roads that you have to drive on or the buses that pick some up. This shows that we all need to take the responsibility and make sure that we leave our house in time to get to school. This doesn't mean rush to school, you don't have a one tardy thing. Three chances in each of your eight classes, that is how many times you can be late. Most kids don't want to be late due to the ISS or teachers jobs that are assigned. I know many kids that would love to have no tardy policy, but if that happened no one would show up for class always being late. They abuse it.
As you said life happens and while yes you should take care to arrive on time. I don't feel you should have to be punished for something outside of your control especially not with something that goes on your record. While there may not be a consequence for your first time of being tardy if you had several encounters you may be forced to rush to school. Like you stated weather is a big problem where you live and weather is a daily occurrence so it is likely to cause you to be running later more than once. While it is true kids may try to abuse not having a tardy policy it can be required that they have to provide a reason for being late. It's very unlikely that students will be able to come up with enough excuses to be late all the time.
The weather is a big problem, many kids won't rush due to the icy roads and that makes them late. The teachers though know and they themselves have driven those roads, for the first class of the day many kids are late but the teachers don't count it due to it being because of the weather. That is for first class, the rest of the classes the students need to be on time because there is no excuse for them to not be on time. You are already on time to school maybe not to first hour but to the rest of your classes you have to take responsibility in your hands and go to your classes. Why would you want to be late? That time in the beginning of the class is when they tell you the important things do you really want to miss that?
In the other classes there are several legitimate reasons for being late. You may have stayed a little bit after class to talk to a teacher. You may have stopped to ask someone in your class for help with understanding material or you could be the person helping another student. You could have a student as a tutor that you see in the hallway and stop to ask them about another tutoring session and discussing when to schedule it and what you want to go over. You may have needed to use the restroom and perhaps had diarrhea which caused you to be in there a while. The hallways could have been too crowded to get through to your class fast enough. These among other reasons could account for someone being late and should not be punished.