Rising temperatures, melting snow and added rain combined to lead the National Weather Service to call for a flood watch until 5 p.m. Saturday.
The watch covers rivers and creeks in Southwest Idaho and Southeast Oregon.
"Small streams and creeks have the greatest potential to flood at this time," said Valerie Mills, a meteorologist with the National Weather Service in Boise.
Larger rivers, which are running low at this time of year, are better able to absorb added water without problems, she said.
The Malheur River near Vale, Ore., was reported at 5.5 feet at 9:30 Friday morning, according to the Northwest River Forecast Center. The river could reach its flood stage of 9.5 feet in the next day or two, the center said.
Idaho rivers in which water levels are monitored with gauges showed no flood dangers Friday morning.
The Boise River at the Glenwood Bridge in Garden City was at 4.54 feet at 9:45 a.m. It reaches flood stage at 10.2 feet.
The Payette River near Payette was at 6.2 feet at 9:30 a.m., about half of the volume needed to flood its banks. Likewise, the Payette north of Emmett, at 3.2 feet at 9:45 a.m., was less than a third the height needed to flood.
The Boise area can expect about a third of an inch of rain on Friday, Mills said. Snow levels are expected to rise to about 4,900 feet.
"We do have quite a bit of rain coming in," Mills said.
Boise has received 1.24 inches of rain so far this month, more than double the .45-inch average between Feb. 1 and 14, Mills said.
The February average for precipitation is .99 of an inch. That was computed using weather service measurements between 1981 and 2010.
So far this year, 2.04 inches of precipitation have fallen in Boise. That's slightly above the 1.7 inches that is normal for the first six weeks of the year.
Boise typically receives about 11 inches of rain and snow water equivalent annually.
For the rain year, which begins Oct. 1, there had been 4,91 inches of precipitation through Thursday. The normal year to date is 5.34 inches, so the total for this year is .43 inches below average, said Dave Groenert, also a National Weather Service meteorologist in Boise.
Today's forecast calls for continued rain and a high temperature of 43 degrees. The overnight low will be about 38, with high temperatures through Tuesday in the low 40s.