Union Reservoir campground
Union Reservoir
Many nearby tourist attractions are worth exploring, including the Boulder County Fairgrounds, the Boulder Museum of Contemporary Art, and the Longmont Museum and Cultural Center.
The campsite amenities include picnic tables, fire rings, restrooms, and potable water. The camping area has 46 campsites, and reservations can be made up to six months in advance. The designated camping season starts in May and ends in September, and the campground operates on a first-come, first-served basis.
One quirky fact about the Union Reservoir is that it was once named Calkins Lake after an early settler in the area, but the name was changed to Union Reservoir after the Union Ditch Company built a canal to bring water to the lake.
The best time of the year to visit Union Reservoir Camping Area is between June and August, with average temperatures ranging from the 60s to 80s Fahrenheit. However, visitors should note that sudden rainstorms are common during the summer months.
What's on-site at Union Reservoir
Key facilities Snoflo tracks for this campground. Confirm with the operator before booking -- amenities can change seasonally.
Plan your trip down to the hour
Same weather feed Snoflo's iOS app uses -- updated continuously from NOAA / yr.no.
Next 5 days, hour by hour
Temperature line with weather symbols on top, snow + rain accumulation as columns, humidity as a dotted line.
5-day forecast table
Every 3 hours, broken out across temperature, snow, rain, humidity, and wind. Each cell is colour-coded relative to the column min/max so trends jump out at a glance.
| Time | Condition | Temp (°F) | Snow (in) | Rain (in) | Humidity (%) | Wind (mps) | Wind dir |
|---|---|---|---|---|---|---|---|
| Loading detailed forecast… | |||||||
15-day temperature & precipitation
Daily temperatures, snow, and rain projected over the next two weeks. Hover any point for the full breakdown.
Other campgrounds in the area
Snoflo-tracked campsites within driving distance of Union Reservoir, with reservations status.
| Campground | Reservations | Toilets | View |
|---|---|---|---|
| St. Vrain State Park | ✓ | ✓ | → |
| Boulder County Fairground | ✗ | ✗ | → |
| Meadow Park | ✗ | ✗ | → |
| Carter Lake - South Side Campgrounds | ✓ | ✗ | → |
| North Pine Campground | ✗ | ✗ | → |
Nearby streamflow
USGS streamgauges within reach of Union Reservoir -- pulled live from the National Water Information System.
| Streamgauge | Discharge | View |
|---|---|---|
| St. Vrain Creek Below Longmont | -999,999 cfs | → |
| St Vrain Cr Blw Boulder Cr At Hwy 119 Nr Longmont | 71 cfs | → |
| Boulder Creek At Mouth | 0 cfs | → |
| Left Hand Creek At Hover Road Near Longmont | 2 cfs | → |
| St. Vrain Creek At Mouth | 57 cfs | → |
| Boulder Cr At North 75th St Nr Boulder | 37 cfs | → |
Nearby snow depths
NRCS SNOTEL stations within reach of Union Reservoir -- relevant when planning a shoulder-season or alpine trip.
| SNOTEL station | Snowpack | 24h Snowfall | View |
|---|---|---|---|
| Longmont 5.1 E | 0.0 in | 0.0 in | → |
| Longmont 1.8 E | 0.0 in | 0.0 in | → |
| Longmont 1.8 Ene | 0.0 in | 0.0 in | → |
| Longmont 2.1 N | 0.0 in | 0.0 in | → |
| Firestone | 0.0 in | 0.0 in | → |
| Longmont 3.0 Sw | 0.0 in | 0.0 in | → |
Plan a longer trip
The closest parks, lakes, boat launches, and paddle runs so a camping night can grow into a full weekend.
🌳 Parks
More parks →⚓ Boat launches
- Lagerman Trail Boulder County
- Brighton
- Standley Lake Trail Westminster
- Adams County
- Miramonte Road Boulder County
- West 69th Avenue 4700, Westminster
Camping essentials & Leave No Trace
- Pack it in, pack it out
- Take all trash, food scraps, and gear back with you to keep campsites clean and protect wildlife.
- Respect wildlife
- Observe animals from a distance, store food securely, and never feed wildlife to maintain natural behavior and safety.
- Know before you go
- Check weather, fire restrictions, trail conditions, and permit requirements to ensure a safe and well-planned trip.
- Minimize campfire impact
- Use established fire rings, keep fires small, fully extinguish them, or opt for a camp stove when fires are restricted.
- Leave what you find
- Preserve natural and cultural features by avoiding removal of plants, rocks, artifacts, or other elements of the environment.
Set push alerts in the Snoflo app
Save Union Reservoir as a favorite, set a custom threshold (precipitation, snowpack, freezing temperatures), and the iOS app will push the moment conditions cross.
About Union Reservoir
Can I make reservations at Union Reservoir?
This campground does not appear to accept reservations -- it's typically first-come, first-served. Arrive early on summer weekends.
How fresh is the weather data on this page?
The hourly forecast updates throughout the day from the NOAA / yr.no public feeds. Streamflow data is pulled live from USGS streamgauges and snowpack from the NRCS SNOTEL network.
What's the best time of year to visit?
Use the 15-day temperature & precipitation outlook on this page to plan -- pick a window with comfortable temperatures and low precipitation. For longer trips, the 5-day hourly meteogram shows snow + rain accumulation hour-by-hour.
How do I get to Union Reservoir?
Tap Directions in the hero above to open driving directions in Google Maps, or Open in map to center the Snoflo interactive map on the campground.
Can I get alerts when conditions change?
Yes -- alerts are managed through the Snoflo iOS app. Favorite this campground, set a threshold (temperature, snowpack, precipitation), and you'll get a push the moment it crosses.
Other campgrounds near here
Snoflo-tracked campgrounds within driving distance of Union Reservoir.