Page developed via a collaboration between CW3E and CNAP by David Pierce, CW3E Director Marty Ralph, and CNAP PI Dan Cayan.
This page shows the accumulated water year-to-date precipitation for various locations in California and Nevada. Currently included locations are: San Diego county; the state of California; the Northern Sierra eight-station index; the Las Vegas region (Clark County, Nevada); and the Reno/Carson City/Lake Tahoe area straddling the California-Nevada border. Water years start on October 1st and extend through the following September 30th and are numbered by the year of the January of the water year. For example, the period October 1, 2015 to September 30, 2016 is water year "2016", since the January in that period is January 2016.
Values are shown as a percent of normal (mean) accumulation found on the last day of the water year. So, values always start at zero on October 1st and increase gradually over the year (never declining). For example, if the "Current" value is 15% and the "1-day delta" (change) is 1.0%, that means that currently we have accumulated 15% of the total precipitation we usually accumulate over an entire water year, and that yesterday that number was 14%. For a normal year, the "Current" value will end up at 100% at the end of the water year. A dry year will end up below 100%, and a wet year will end above 100%.
Note: Percentile values for the 1-, 2-, and 3-day changes are in percentage points of the mean accumulation in a water year, and are calculated excluding any values of zero (i.e., dry periods are not counted). Also, all rankings (including "record" and percentile values) are done in a centered +/- 45 day seasonal window to account for the fact that the regions included here receive so much more precipitation in winter than in summer.
Data updated 2023/12/19 23:58 Pacific time
San Diego County (station list) (archive of past tables)
| Current: | 7.6% | 1‑day Δ: | 0.00% | 2‑day Δ: | 0.07% | 3‑day Δ: | 0.07% |
| -------- | -------- | -------- | -------- | -------- | -------- | -------- | -------- |
| (2017/12/19) | |||||||
| Rec_low: | 0.8% | 50‑ptile: | 0.48% | 50‑ptile: | 0.83% | 50‑ptile: | 1.09% |
| Typ_low: | 8.1% | 90‑ptile: | 3.80% | 90‑ptile: | 5.78% | 90‑ptile: | 7.47% |
| Mean: | 21.7% | 95‑ptile: | 5.78% | 95‑ptile: | 8.67% | 95‑ptile: | 10.53% |
| Typ_high: | 32.8% | 99‑ptile: | 10.16% | 99‑ptile: | 16.00% | 99‑ptile: | 20.17% |
| Rec_high: | 72.5% | Record: | 26.67% | Record: | 33.02% | Record: | 40.03% |
| (1965/12/19) | (1965/11/23) | (1965/11/23) | (1966/12/07) |
Greater Los Angeles Region (station list) (archive of past tables)
| Current: | 5.8% | 1‑day Δ: | 1.54% | 2‑day Δ: | 1.79% | 3‑day Δ: | 1.79% |
| -------- | -------- | -------- | -------- | -------- | -------- | -------- | -------- |
| (2017/12/19) | |||||||
| Rec_low: | 0.4% | 50‑ptile: | 0.28% | 50‑ptile: | 0.44% | 50‑ptile: | 0.61% |
| Typ_low: | 6.4% | 90‑ptile: | 4.29% | 90‑ptile: | 6.45% | 90‑ptile: | 8.06% |
| Mean: | 21.6% | 95‑ptile: | 6.52% | 95‑ptile: | 10.12% | 95‑ptile: | 12.45% |
| Typ_high: | 34.9% | 99‑ptile: | 11.16% | 99‑ptile: | 18.61% | 99‑ptile: | 21.97% |
| Rec_high: | 75.8% | Record: | 24.10% | Record: | 45.04% | Record: | 51.69% |
| (1965/12/19) | (1943/01/22) | (1943/01/23) | (1943/01/24) |
All California (station list) (archive of past tables)
| Current: | 16.1% | 1‑day Δ: | 2.36% | 2‑day Δ: | 5.49% | 3‑day Δ: | 5.67% |
| -------- | -------- | -------- | -------- | -------- | -------- | -------- | -------- |
| (1959/12/19) | |||||||
| Rec_low: | 1.7% | 50‑ptile: | 0.19% | 50‑ptile: | 0.39% | 50‑ptile: | 0.68% |
| Typ_low: | 15.8% | 90‑ptile: | 2.17% | 90‑ptile: | 3.78% | 90‑ptile: | 5.16% |
| Mean: | 27.4% | 95‑ptile: | 3.04% | 95‑ptile: | 5.17% | 95‑ptile: | 6.97% |
| Typ_high: | 41.0% | 99‑ptile: | 4.78% | 99‑ptile: | 8.28% | 99‑ptile: | 10.87% |
| Rec_high: | 55.4% | Record: | 9.02% | Record: | 15.62% | Record: | 20.93% |
| (1970/12/19) | (1943/01/21) | (1955/12/23) | (1943/01/23) |
Northern Sierra Nevada 8-Station Index (station list; a traditional indicator of CA water supply) (archive of past tables)
| Current: | 17.8% | 1‑day Δ: | 3.25% | 2‑day Δ: | 6.34% | 3‑day Δ: | 6.38% |
| -------- | -------- | -------- | -------- | -------- | -------- | -------- | -------- |
| (1959/12/19) | |||||||
| Rec_low: | 1.1% | 50‑ptile: | 0.32% | 50‑ptile: | 0.61% | 50‑ptile: | 0.92% |
| Typ_low: | 16.7% | 90‑ptile: | 2.55% | 90‑ptile: | 4.20% | 90‑ptile: | 5.76% |
| Mean: | 29.0% | 95‑ptile: | 3.47% | 95‑ptile: | 5.81% | 95‑ptile: | 7.67% |
| Typ_high: | 43.6% | 99‑ptile: | 5.71% | 99‑ptile: | 9.32% | 99‑ptile: | 11.82% |
| Rec_high: | 69.1% | Record: | 13.52% | Record: | 20.73% | Record: | 27.18% |
| (1950/12/19) | (1964/12/22) | (1964/12/23) | (1964/12/23) |
Clark County Nevada (Las Vegas) regional index (station list) (archive of past tables)
| Current: | 2.6% | 1‑day Δ: | 0.18% | 2‑day Δ: | 0.18% | 3‑day Δ: | 0.18% |
| -------- | -------- | -------- | -------- | -------- | -------- | -------- | -------- |
| (1999/12/19) | |||||||
| Rec_low: | 0.0% | 50‑ptile: | 0.60% | 50‑ptile: | 0.83% | 50‑ptile: | 1.02% |
| Typ_low: | 4.1% | 90‑ptile: | 5.31% | 90‑ptile: | 7.25% | 90‑ptile: | 8.73% |
| Mean: | 20.4% | 95‑ptile: | 7.51% | 95‑ptile: | 10.85% | 95‑ptile: | 13.25% |
| Typ_high: | 36.6% | 99‑ptile: | 13.27% | 99‑ptile: | 18.52% | 99‑ptile: | 21.80% |
| Rec_high: | 70.4% | Record: | 26.10% | Record: | 38.78% | Record: | 46.53% |
| (1987/12/19) | (2004/12/29) | (2004/12/29) | (2010/12/23) |
Reno/Carson City Nevada regional index (station list) (archive of past tables)
| Current: | 22.9% | 1‑day Δ: | 1.01% | 2‑day Δ: | 3.84% | 3‑day Δ: | 3.93% |
| -------- | -------- | -------- | -------- | -------- | -------- | -------- | -------- |
| (1959/12/19) | |||||||
| Rec_low: | 0.6% | 50‑ptile: | 0.50% | 50‑ptile: | 0.78% | 50‑ptile: | 1.03% |
| Typ_low: | 11.3% | 90‑ptile: | 3.47% | 90‑ptile: | 5.16% | 90‑ptile: | 6.62% |
| Mean: | 24.7% | 95‑ptile: | 5.12% | 95‑ptile: | 7.98% | 95‑ptile: | 10.07% |
| Typ_high: | 37.6% | 99‑ptile: | 10.25% | 99‑ptile: | 14.83% | 99‑ptile: | 18.29% |
| Rec_high: | 77.6% | Record: | 23.54% | Record: | 36.33% | Record: | 45.11% |
| (1950/12/19) | (1943/01/21) | (1943/01/22) | (1955/12/24) |
The underlying data is primarily GHCN daily, augmented over the last few days by real-time gauge data assembled by the California-Nevada River Forecasting Center. Accordingly, the data primarily have a daily resolution. 1-Day changes, then, signify the difference between the accumulated value at the beginning of the current day and the current hour of the current day. In other words, it is not a change over 24 hours, but rather the change over the current calendar day. Similarly, the 2- and 3-day changes are over calendar days, not over 48 and 72 hours, respectively.
Because the gauge data is real-time, errors can and do occur in it. Later updates can change the preliminary numbers. After the real-time gauge data is ingested into the quality-controlled GHCN daily dataset, the numbers should become more reliable. Depending on the station, it can take anywhere from a day to a few weeks for data to appear in the GHCN daily data set. During this time, the numbers on this page will be influenced by the real-time gauge data.
The "typical" range encompasses the central 2/3rds of the data.
So the "typcial low" value is the 16.7th percentile value,
and the "typical high" value is the 83.3rd percentile value.