Water Temperature

Water Quality Measurement  | Physical Parameter

Lake Pend Oreille | Pend Oreille River

Keeping our waters Swimmable, Fishable, and Drinkable

Water temperature is especially important for recreational uses, such as swimming and fishing. Our water quality data helps us keep Lake Pend Oreille and the surrounding waterways swimmable, fishable, and drinkable for future generations. Using our volunteer citizen science based monitoring programs, we work to preserve the health of our waterways.


Swim Guide  |  Fishing Planner Get Involved

Temperature is a great baseline measurement that is often correlated to many other water quality parameters. For example, warmer water generally dissolves less oxygen than cold water, which means that less oxygen is available for use by aquatic organisms like fish in warm water.

Many of our native fish species, like the endangered Bull Trout, require cool, oxygen-rich water to live in. Warm water can also promote excessive growth of algae and aquatic plants.  Our guideline, or recommended maximum temperature for healthy aquatic ecosystems, is based on the Idaho Department of Environmental Quality’s water quality standards.

On our Water Temperature graph, the individual data points represent a single temperature taken. The temperature for each site is taken at the depth of the secchi disk, or where the water become less transparent. There may be some duplicate temperatures for the sites, so there is likely to be overlap of data points.

We take the temperature of the water each time we collect data – once a month for five months out of the year (June – October). The bars represent the upper quartile (75% of the temperatures taken at this site fall below this line), the median (or mid-point of the data) temperature for each site, first quartile (25% of the temperatures taken at this site fall below this line), and the box represents the middle 50% of the data.

Variance between sites is likely due to their location on the lake. Some sites, such as along the Pend Oreille River, are mixed more and therefore are cooler. Some sites, such as the sloughs, are more stable and therefore have warmer temperatures in the summer. 

Use our interactive graph to check out all the data we have collected and the averages in both Fahrenheit and Celsius. Hover over a data point to see more information or try clicking on the name of a month in the All Data graph to see all the data for just one month! 

Support this Program!

Laboratory analysis of water samples are very expensive totalling about $1,000 per station per field season. Your donation helps cover the costs of collecting & analyzing water samples.

Become a Citizen Scientist!

Become a trained citizen scientist. Collecting water samples is a great way to enjoy time on the water & get involved in active stewardship of our local waterways!