Preheat your oven to 250°F (120°C).
In a large mixing bowl, combine the Rice Chex cereal, Corn Chex cereal, pretzels, and cashews. Stir gently until everything is evenly mixed.
In a separate small bowl, whisk together the melted butter, dill pickle juice, garlic powder, onion powder, dill weed, salt (if using), black pepper, and dill pickle seasoning (if desired).
Pour the butter mixture over the Chex mix. Gently stir until all pieces are coated evenly.
Spread the mixture evenly onto a baking sheet lined with parchment paper or a silicone baking mat. Bake in your preheated oven for about 45 minutes, stirring every 15 minutes.
Once golden and crispy, remove the baking sheet from the oven and let it cool completely on the sheet.
Once cooled completely, transfer your Dill Pickle Chex Mix into an airtight container at room temperature.