All seasons are there on earth due to axis tilt. If the earth had no axis tilt, there would be no season. This means there would be much less variation in climate at any particular place on the earth’s surface. The equator would always be the hottest place on earth instead of what we currently experience. The coldest places would always be the poles. The regions closer to the poles would still be colder, not due to the length of the day but mainly due to the angle of the sun’s rays as they fall on the surface. There would no longer be an arctic circle or an antarctic circle and no regions on earth where we would get light or dark for more than a day. All places would have 12 hours of the day and 12 hours of the night.