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Weather for Boise, Idaho

Lat: 43.61N, Lon: 116.23W
Wx Zone: IDZ014 CWA Used: BOI

Idaho Drought Monitor

The Idaho Drought monitor is a subset of the United States Monitor, issued every Thursday morning, based on drought conditions the previous Tuesday. The map below shows the current drought level around the state, and the percent of Idaho land area in each drought level compared to the previous week.

Read an explanation of the drought intensities and what they mean.

Idaho Drought Monitor

Idaho Hydrologic Information Statement

Note that if drought conditions are not being experienced, or in the case of river flooding or heavy rain, this statement may be used to indicate river flows or flood potential.

FGUS75 KBOI 141630

Water Supply Outlook 
National Weather Service Boise ID
1030 AM MDT Fri Apr 14 2017


The spring flood risk due to snowmelt is above average to well above 
average across most of southern Idaho, with areas of greatest 
concern being the Central Mountains and southeast Idaho. For 
northern Idaho, the spring flood risk is generally above average.

Mid and high elevation snowpack remains exceptional across much of 
southern Idaho. In fact, snowpack is at record or near record levels 
across portions of the Central Mountains. Meanwhile, early April 
snowpack is around normal across northern Idaho. Wet conditions 
through the winter and early spring have left soils very moist and 
streamflows running high, which sets the stage for above average 
flood risk across the majority of the state through the spring 

The primary factors in the development of spring flooding are the 
occurrence of persistent above normal temperatures, and rain on snow 
precipitation events. Even for areas that have low snowpack, spring 
flooding is possible under the right scenario. Additionally, burn 
scars can have a significant impact on local flood potential during 
spring snowmelt. 

Water Supply 
National Weather Service April through September water supply volume 
forecasts across southern Idaho vary from 100 to 260 percent of 
average. However, volume forecasts for the majority of southern 
Idaho locations exceed 150 percent of normal and several rank within 
the top 5 based on historical record from 1971 to 2016. Across the 
northern half of Idaho, volume forecast percentages are generally 
100 to 150 percent of average for the April through September 
period. Mountain snowpack in Idaho typically peaks in early April, 
and these forecasts will fluctuate some over the next couple of 
months based on spring precipitation. 

Precipitation and Temperature
As of April 11, Water Year precipitation was well above normal 
across most of Idaho. Percentages were highest across the Panhandle, 
Central Mountains, south-central and southeast Idaho, where 150 to 
300 percent of normal precipitation has fallen since October 1, 
2016. Lowest percentages in the state were generally across west-
central and far southwest Idaho at 110 to 150 percent of normal. 
Average temperatures have been a little cooler than normal across 
northern and west-central Idaho. Elsewhere across the state, 
temperatures have generally been average or a little above average 
for the Water Year. 

As of April 12, snowpack across the southern half of Idaho was above 
normal, with exceptional snowpack remaining across portions of the 
Central Mountains and southeast Idaho. According to NRCS SNOTEL 
data, portions of the Central Mountains were holding record or near 
record amounts of high elevation snow. Basin snowpack percentages 
ranged from 103 to 189 percent of median across southern Idaho, with 
the Big Wood, Little Wood, and Big Lost Basins carrying the highest 
percentages at 180 to 189 percent of median. Across northern Idaho, 
snowpack percentages were around 100 percent of median. Mountain 
snowpack for Idaho as a whole typically peaks in early April. 

Basin-wide reservoir summaries as of April 1 vary from near average 
storage to well above average storage across Idaho. Large inflows on 
the Owyhee System in February and March boosted reservoir levels 
such that water was being released through Owyhee Dam's Glory Ring 
Gate. The last couple of times this occurred were in 2011, and prior 
to that it was 2006. Weather patterns, irrigation demand, and flood 
control operations will drive reservoir operations over the next few 
months. With the large snowpack remaining across much of southern 
Idaho, above average reservoir outflows and high river levels are a 
good bet through the spring. 

Abundant autumn rain and good winter snowpack have erased drought
conditions across the state according to the U.S. Drought Monitor.
Weather and precipitation through the spring will determine whether 
or not conditions continue to improve before heading into the warm 
and dry season. The U.S. Seasonal Drought Outlook suggests that 
drought conditions are not likely to return to Idaho through the 

Long Range Outlook
The outlook for April, May, and June indicates equal chances of 
above normal, normal, or below normal temperatures across Idaho, 
except for extreme southeast Idaho where above normal temperatures 
are slightly favored. Probabilities slightly favor above normal 
precipitation during the period for areas of Idaho near the Montana 
border, with equal chance of above normal, normal, or below normal 
precipitation elsewhere.  

Refer to the links provided below for the latest information on 
water resources.

Water Supply Volume Forecasts
National Weather Service-Northwest River Forecast Center

National Weather Service-Colorado Basin River Forecast Center

Snowpack Information
National Weather Service-Northwest River Forecast Center

National Weather Service-National Operational Hydrologic Remote 
Sensing Center

USDA-Natural Resources Conservation Service

Reservoir Storage
Bureau of Reclamation

USDA-Natural Resources Conservation Service

Drought Conditions
U.S. Drought Portal

U.S. Drought Monitor

National Drought Mitigation Center

Peak Flow Forecasts
Northwest River Forecast Center

Colorado Basin River Forecast Center

Temperature and Precipitation Outlook
Climate Prediction Center