The Eastern Montana Stream Temperature Regression (EMonSTeR) is an expansion and update of the popular NorWeST stream temperature model produced by Dan Isaak and others at the U.S. Forest Service. NorWeST uses stream temperature data collected by hundreds of scientists throughout the western United States to estimate mean August stream temperatures. These estimates are applied across the entire, inter-connected system of perennial streams for which data is available. What is particularly useful for aquatic biologists is that NorWeST can then use climate change scenarios to determine what stream temperatures are likely to be in the future. These projections can then be used to determine where fish and other stream-dwelling species will be able to persist as water temperatures increase (e.g. Cold-Water Climate Shield) – these areas are called “climate refugia.”

NorWeST stream temperature map.

Stream temperature data was last gathered for Montana in 2011. At that time, large parts of eastern Montana, in the Missouri and Yellowstone River basins, did not have enough data available for NorWeST to accurately estimate mean August stream temperatures. In order to determine what streams will serve as climate refugia for all of Montana’s native aquatic species, this missing piece is critical to include. That is why I am collecting stream temperature data from the Yellowstone & Missouri basins and the U.S. Forest Service will re-run the NorWeST model for this region.

How can you help?

1) Send Previously Collected Data


  • From streams in the Yellowstone or Missouri River basins of Montana (see map).
  • Temperature logger (Onset HOBO or similar) data w/ multiple daily readings.
  • Must be from 2012 – present. Summer 2020 data is great.
  • Must contain data from at least 28 days in August.
  • Please send data as a CSV or Excel file where each individual reading has a Date, Time-stamp, and temperature in degrees celsius or fahrenheit to Please include the stream name and logger coordinates (in decimal-degrees).

2) Deploy Your Loggers!

Have temperature data loggers that wouldn’t otherwise be in use during 2020? Consider putting it out there! If you don’t already have a site chosen, please contact me so I can suggest locations that will be particularly useful: (406) 214-9010 or

3) Volunteer to Deploy One or More of My Loggers

I have about 90 Onset HOBO temperature loggers I will need help deploying this summer (2020). Streams without previously collected temperature data will be prioritized but location is somewhat flexible. I need the logger to be recording for all of August but you are welcome to deploy loggers anytime after runoff and leave in the field until ice forms. If you are willing to help, please contact me.

Onset HOBO temperature logger
EMonSTeR is part of the Refugia project. To learn more, click on the logo.