For a low-key, and inexpensive pitstop just miles over the California border, pull over at Castle Crags State Park. There's a beautiful picnic area just across the river from the main entrance (that would be the upper Sacramento River) and forest groves to explore. If you plan ahead, you can stop a few miles north in Dunsmuir for sandwiches. The park gets its name from the 6,000-feet tall glacier-polished crags visible from the freeway. You can hike to them, but there are two easier 1-mile hiking trails that may be better suited for a quick stop: Indian Creek Trail and Root Creek Trail, which ends at Root Creek (great to play in). Both begin near the picnic grounds (grab a map while entering the park).
In the summer, Castle Crags is a much less crowded option than nearby Lake Shasta, and often your last cool pit-stop before entering the blisteringly hot Redding area and Sacramento Valley.