Hello~Your blood sugar could have been low at those times, that can cause dizziness and balance issues. I would have a A1C blood test run to see where your numbers are, and, in the meantime, eat even a small bit of food to keep the blood sugar more balanced. It is not always easy in heat, but better to be safe than sorry. Oh, and another thing, make sure you are well hydrated, if possible, take a bottle of water on your walk.