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River Sioux, IA Weather
River Sioux, Iowa sits at 41.8024, -96.0480. Its warmest month is July, when the day usually reaches 86F, and its coldest is January, when the night usually falls to 9F. May is the wettest, with rain on about 14 days. The hottest day in the station record is 105F on July 24, 2012, and the coldest night -31F on February 17, 2021. This page carries live conditions, an hour by hour timeline, a ten day outlook, radar, monthly averages and searchable daily history back to 1940.
About River Sioux weather
River Sioux sits at 41.8024, -96.0480 and covers about 0.381 square miles. The forecast above is live: current conditions lead with the HRRR model, corrected against the nearest reporting station and against radar overhead, because a model can lag a storm and the radar cannot.
The tabs at the top of this page carry the hour by hour timeline, the ten day outlook and live radar. Where the models disagree about a day, the rock says so on the day rather than quietly picking a winner.
The rock grades itself against what actually happened and publishes the result whether it flatters it or not. Those standings live in the Receipts.
- Current conditions and forecast: NOAA forecast grids (the National Weather Service digital forecast, the National Blend of Models, HRRR and GFS) decoded on our own server, corrected against the nearest reporting station and our own radar. Open-Meteo is consulted only as a fallback when our server is silent.
- Warnings and alerts: the National Weather Service, passed through unchanged.
- Radar: NOAA MRMS merged reflectivity, rendered into tiles by myweatherrock.
- Monthly averages and records: computed by myweatherrock from NOAA GHCN-Daily station records at the nearest qualifying station, named on this page with its distance. Measurements, not estimates.
- Daily history search: the town's own NOAA GHCN-Daily station file, held on our server, measurements by day. Months the station missed fall back to the Open-Meteo historical archive (reanalysis), and the page says so when it does.
What the weather is usually like in River Sioux
River Sioux is warmest in July, when the day usually reaches 86F, and coldest in January, when the night usually falls to 9F. May is the wettest month, with rain on about 14 days of it.
The same year as numbers
| Month | Usual high | Usual low | Rain days | Snow days |
|---|---|---|---|---|
| January | 30F | 9F | 8 | 7 |
| February | 32F | 11F | 8 | 7 |
| March | 49F | 25F | 9 | 4 |
| April | 62F | 35F | 10 | 2 |
| May | 73F | 48F | 14 | 0 |
| June | 83F | 59F | 13 | 0 |
| July | 86F | 62F | 10 | 0 |
| August | 84F | 60F | 10 | 0 |
| September | 78F | 51F | 9 | 0 |
| October | 64F | 37F | 9 | 1 |
| November | 49F | 24F | 6 | 2 |
| December | 34F | 14F | 7 | 6 |
Thirty-year normals, 1991 to 2020, computed from the daily record, measured at the Little Sioux 2Nw station 1.7 miles away. A rain day means at least a hundredth of an inch fell, the same measurable-precipitation mark the Weather Service uses. Source: computed from the station record, NOAA GHCN daily.
River Sioux weather history, back to 1940
Pick any month back to 1940 and see what the archive holds for River Sioux: the reanalysis record of what happened, day by day.
Reading this month last year to start you off.
River Sioux weather records
In 34,286 days of observations River Sioux has been as hot as 105F and as cold as -31F. Not averages: the actual days.
NOAA GHCN daily station records, observed 2002 to 2026: temperature at the Little Sioux 2Nw station, 1.7 miles away. Station measurements, not estimates. Record dates reflect the station's own observation schedule, and the official state record may live at a different station.
Common questions about River Sioux weather
What is the weather usually like in River Sioux, IA?
River Sioux is warmest in July, when the day usually reaches 86F, and coldest in January, when the night usually falls to 9F. Rain falls on roughly 113 days a year, most often in May. Averages are thirty-year normals, 1991 to 2020, computed from the nearest NOAA station's own daily record.
How much does it rain in River Sioux, IA?
About 113 days a year see at least a hundredth of an inch, which is the Weather Service's measurable-precipitation mark. May is the wettest month with rain on about 14 of its days, and November the driest with about 6.
Does it snow in River Sioux, IA?
Yes. Snow falls on about 29 days a year, most often in January, which averages about 7 snowy days. Those are days with measurable snowfall, not days with snow lying on the ground.
What is the hottest it has ever been in River Sioux, IA?
The hottest day measured for River Sioux reached 105F on July 24, 2012, and the coldest night -31F on February 17, 2021. Both are real NOAA station measurements from the GHCN daily archive, observed 2002 to 2026, at the Little Sioux 2Nw station. Not estimates, though the official state record may live at a different station.
Can I look up past weather for River Sioux, IA?
Yes, and for free. The History tab on this page takes any month back to 1940 and shows every day of it: the high, the low, what fell, and that month's hottest and coldest day. No account and no payment.
Is the River Sioux forecast on this page free, and does it track me?
It is free, carries no advertising, and needs no account. Nothing about a visitor leaves the device except the coordinates needed to fetch a forecast, and those are not stored against anyone.