According to Grizzly Hackle, mornings are the only good fishing time of the day for the Clark Fork, and they rated it a 3 out of 5 for fishing:
The Clark Fork is fishing well only in the mornings at this point. It’s getting warm with temps over 70 near Superior most days. Let’s hope for some cooler nights. The terrestrial fishing in the mornings when the water temps are down is good and hoppers are the way to go. There are still some PMD’s, PED’s, Caddis around with fish sipping in the foam lines. Until we see Trico’s the match the hatch type fishing will be so/so. Dropper fishing has been good as well with jig nymphs and perdigons. Get out early and be done fishing by 2 pm. There isn’t any restrictions out there, but the water is too warm in the afternoons/evenings to be safe for fishing.