I don't mean to sound like a smart a$$ here but teddy grahms, pretzels, and fig newtons are healthy? Don't bet on it.
This is summer and farm markets are FULL of amazing fresh local produce.
Try blueberries, peaches, plums, cherries...you name it. all delicious and in season.
Try whole wheat NO SUGAR, no hydrogenated oil containing crackers or other whole grain crackers with low or no added salt.
Try Heritage Brand O's (no salt or sugar) or Spelt or Kamut flakes for a crunchy snack.
Make fresh popcorn the old fashioned way. (heat oil, pop etc in a heavy pan)
Unsalted Rice Cakes
Raw nuts...like macadamia almonds or walnuts
Dried non salted Pumpkin seeds
If you can use a cooler, whole milk organic yogurt, cheese, or almond butter makes a healthy protein packed treat.
also, don't forget the classics like celery sticks and carrot sticks.
Amd in this heat...WATERMELON!