Since the weather here seems to be rain, rain and more rain the next few days, let's dive into some references to rain in the journals:

From Bradbury:
31st.-The morning was rainy, and was succeeded by a strong north wind, which caused a sudden
change in the temperature of the weather: the 30th had been warm, but this night the water, in a
tin cup of a pint measure, that had been left full in the boat, was found to be nearly all solid ice on
the morning of the first of April.

16th.- We began to notice more particularly the great number of drowned buffaloes that were
floating on the river; vast numbers of them were also thrown ashore, and upon the rafts, on the
points of the islands. The carcases had attracted an immense number of turkey buzzards, (vultur
aura) and as the preceding night had been rainy, multitudes of them were sitting on the trees,
with their backs towards the sun, and their wings spread out to dry, a common practice with these
birds after rain.

From Francois Antoine Larocque:
Wednesday 5th. We followed the Green River till eleven o’clock when we arrived at the woods,
where being an appearance of rainy weather we encamped. There was no Buffalo in seight. At 12
it began to rain and continued hard and uninterruptedly until next morning. Here we saw plenty
of wild fowls, Ducks, Bustards, Geese, Swans, &c., and killed a number of them.
Thursday 6th. There being an appearance of fine weather, we sat off and walked about three miles,
when the weather being cloudy we stopped to encamp, but before we could make a hut for our
goods the rain began again, and fell amasingly hard so that in a few hours every hollows or valley
in the plains were full of water, and every brook or creek was swellen to rivers. There were plenty
of Buffaloes and the rain ceasing in the evening we killed a very fat young bull and a fat Elk deer.
At night the rain began again and continued without intermission until morning.

From Harrison Rogers:
SUNDAY, JUNE 1ST, 1828. We got our horses about 10 o.c. A.M. and packed up and started in
the rain, as it had not quit from the time it commenced yesterday, directing our course west, up a
steep and brushy mountain, and travelled about 3 miles and enc. in a small bottom pararie, principally
covered with ferns; the travelling amazing bad; we left several packs of fur on the road and
lost several pack horses and some loose horses, the day being so rainy that it was almost impossible
to get up and down the mountains; the road became quite mirery and slippery. Capt. Smith
got kicked by a mule and hurt pretty bad. When I reached camp with the rare [rear], it was night,
and all hands very wet and tired.

Storm: Waiting for the Caravan by Alfred Jacob Miller.

For sure Leftlane, they were tough hombres.

Here's a great quote from Russell, after a "dinner" of bison roasted over a sage fire:

After supper (if I may be allowed to disgrace the term by
applying it to such a Wolfish feast) we spread the Bull skin down in the mud in the dryest place
we could find and laid down upon it. Our fire was immediately put out by the rain and all was
Egyptian darkness. We lay tolerably comfortable whilst the skin retained its animal warmth and
remained above the surface but the mud being soft the weight of our bodies sunk it by degrees
below the water level which ran under us on the skin but we concluded it was best to lie still and
keep the water warm that was about us for if we stirred we let in the cold water and if we removed
our bed we were more likely to find a worse instead of a better place as it rained very hard all
night.

Harrison Rogers journal entry was from southern Oregon. A month and a half later he would be dead along with most of the rest of Smith's men at the hands of the Umpqua Indians.

That entire trip was definitely not one of the more economically successful "hunts".

It could be northern California that the Roger's journal entry came from. They called the large river they crossed there the "Indian Scalp" river. Possibly the Klamath?