Temperature

The recently released TopoWx ("Topography Weather", pronounced “twix”) dataset provides the best representation of interpolated temperature for Montana.  Developed at the University of Montana for the conterminous U.S., TopoWx provides an 800-meter interpolation of minimum and maximum topo-climatic air temperature for the years 1948 to 2014 with measures of uncertainty. TopoWx is the source for all temperature related map products presented in this atlas.

Click on a heading below to expose the information for that topic heading.

Annual Temperatures

Mean annual temperatures for the years 1981-2010Online map of mean annual temperature (Web application)

Online map of annual mean, minimum, and maximum temperatures (Web application)

Image of mean annual temperature map (JPEG)

Print version of mean annual temperature map (PDF)

Mean annual temperature for the years 1981-2010 from TopoWx. TopoWx was recently completed at the University of Montana. Mean temperature is derived from minimum and maximum temperature, which are interpolated from climate stations using elevation-based variables and satellite data as predictors of air temperature.

For each 800-meter square area in the area-of-interest the daily interpolated minimum and maximum temperature were averaged for each day in the period 1948 through 2012 to create a daily mean temperature product.  The daily mean temperatures within a year were averaged to obtain the mean temperature for each year in the period 1981 through 2010.  The 30-year annual mean was calculated from the annual mean for all years in the period 1981-2010.

Content Credits:

Mean minimum temperature for the years 1981-2010

Online map of mean minimum temperature (Web application)

Online map of annual mean, minimum, and maximum temperatures (Web application)

Image of mean annual minimum temperature map (JPEG)

Print version of mean annual minimum temperature map (PDF)

Mean annual minimum temperature for the years 1981-2010 from TopoWx. TopoWx was recently completed at the University of Montana. Minimum temperatures are interpolated from climate stations using elevation-based variables and satellite data as predictors of air temperature.

For each 800-meter square area in the area-of-interest the daily interpolated minimum temperatures within a year were averaged to obtain the mean minimum temperature for each year in the period 1981 through 2010.  The 30-year annual mean was calculated from the annual mean for all years in the period 1981-2010.

Content Credits:

Online map of mean annual maximum temperature

Online map of mean annual maximum temperature (Web application)

Online map of annual mean, minimum, and maximum temperatures (Web application)

Image of mean annual maximum temperature map (JPEG)

Print version of mean annual maximum temperature map (PDF)

Mean annual maximum temperature for the years 1981-2010 from TopoWx. TopoWx was recently completed at the University of Montana. Maximum temperatures are interpolated from climate stations using elevation-based variables and satellite data as predictors of air temperature.

For each 800-meter square area in the area-of-interest the daily interpolated maximum temperatures within a year were averaged to obtain the mean maximum temperature for each year in the period 1981 through 2010.  The 30-year annual mean was calculated from the annual mean for all years in the period 1981-2010.

Content Credits:

Online map of minimum minimum temperature

Online map of minimum minimum temperature (Web applicaton)

Online map of annual mean, minimum, and maximum temperatures (Web application)

Image of minimum minimum temperature map (JPEG)

Print version of minimum minimum temperature map (PDF)

The minimum minimum temperature for the years 1981-2010 from TopoWx. TopoWx was recently completed at the University of Montana. Minimum temperatures are interpolated from climate stations using elevation-based variables and satellite data as predictors of air temperature.

For each 800-kilometer square area in the area-of-interest the daily interpolated minimum temperature was assessed to determine if it was the lowest minimum temperature across years 1981-2010. The map represents the minimum temperature found across all years for each 800-kilometer square area for the period 1981-2010.

Content Credits:

Online map of maximum maximum temperature

Online map of maximum maximum temperature (Web application)

Online map of annual mean, minimum, and maximum temperatures (Web application)

Image of of maximum maximum temperature map (JPEG)

Print version of maximum maximum temperature map (PDF)

The maximum maximum temperature for the years 1981-2010 from TopoWx. TopoWx was recently completed at the University of Montana. Maximum temperatures are interpolated from climate stations using elevation-based variables and satellite data as predictors of air temperature.

For each 800-kilometer square area in the area-of-interest the daily interpolated maximum temperature was assessed to determine if it was the highest maximum temperature across years 1981-2010.  The map represents the maximum temperature found across all years for each 800-kilometer square area for the period 1981-2010.

Content Credits:

Monthly Temperatures

Online map of monthly mean temperature

Online map of mean monthly temperature (Web application)

Image of mean monthly temperature map (JPEG)

Print version of mean monthly temperature map (PDF)

Mean monthly temperature for the years 1981-2010 from TopoWx. TopoWx was recently completed at the University of Montana. Minimum and maximum temperatures are interpolated from climate stations using elevation-based variables and satellite data as predictors of air temperature.

For each 800-meter square area in the area-of-interest the daily interpolated minimum and maximum temperature were averaged for each day in the period 1981 through 2010 to create a daily mean temperature product.  The daily mean temperatures within a month were averaged to obtain the mean temperature for each month within each year in the period 1981 through 2010.  The 30-year annual mean was calculated from the annual monthly mean for all years in the period 1981-2010.

Content Credits:

Online map of mean monthly minimum temperature

Online map of mean monthly minimum temperature (Web application)

Image of mean monthly minimum temperature map (JPEG)

Print version of mean monthly minimum temperature map (PDF)

Mean monthly minimum temperature for the years 1981-2010 from TopoWx. TopoWx was recently completed at the University of Montana. Minimum temperatures are interpolated from climate stations using elevation-based variables and satellite data as predictors of air temperature.

For each 800-meter square area in the area-of-interest the daily interpolated minimum temperatures within a month were averaged to obtain the mean minimum temperature for each month within each year in the period 1981 through 2010.  The 30-year annual mean was calculated from the annual monthly mean for all years in the period 1981-2010.

Content Credits:

Online map of mean monthly maximum temperature

Online map of mean monthly maximum temperature (Web application)

Image of mean monthly maximum temperature map (JPEG)

Print version of mean monthly maximum temperature map (PDF)

Mean monthly maximum temperature for the years 1981-2010 from TopoWx. TopoWx was recently completed at the University of Montana. Maximum temperatures are interpolated from climate stations using elevation-based variables and satellite data as predictors of air temperature.

For each 800-meter square area in the area-of-interest the daily interpolated maximum temperatures within a month were averaged to obtain the mean maximum temperature for each month within each year in the period 1981 through 2010.  The 30-year annual mean was calculated from the annual monthly mean for all years in the period 1981-2010.

Content Credits:

Growing Season from Temperature

Online map for date of last freeze

Online map of mean date of last freeze (Web application)

Online map of growing season (Web application)

Image of mean date of last freeze map (JPEG)

Print version of mean date of last freeze map (PDF)

Mean date of last freeze for the years 1981-2010 from TopoWx. TopoWx was recently completed at the University of Montana. Minimum temperatures are interpolated from climate stations using elevation-based variables and satellite data as predictors of air temperature.

Starting from January 1st for each 800-kilometer square area in the area-of-interest the daily interpolated minimum temperature was assessed to determine if it was the last day in that year the temperature was less than 32 degrees Fahrenheit for each year in the period 1981-2010. The Julian day was recorded for each 800-kilometer square area when that event occurred.  The 30-year annual mean was calculated from the last-freeze dates for all years in the period 1981-2010.

Content Credits:

Online map of mean date of first freeze

Online map of mean date of first freeze (Web application)

Online map of growing season (Web application)

Image of mean date of first freeze map (JPEG)

Print version of mean date of first freeze map (PDF)

Mean date of first freeze for the years 1981-2010 from TopoWx. TopoWx was recently completed at the University of Montana. Minimum temperatures are interpolated from climate stations using elevation-based variables and satellite data as predictors of air temperature.

Starting from July 1st for each 800-kilometer square area in the area-of-interest the daily interpolated minimum temperature was assessed to determine if it was the first day in that year for the temperature to be less than 32 degrees Fahrenheit for each year in the period 1981-2010. The Julian day was recorded for each 800-kilometer square area when that event occurred.  The 30-year annual mean was calculated from the first-freeze dates for all years in the period 1981-2010.

Content Credits:

Online map for mean number of frost-free days

Online map of mean number of frost-free days (Web application)

Online map of growing season (Web application)

Image of mean number of frost-free days map (JPEG)

Print version of mean number of frost-free days map (PDF)

Mean number of frost-free days for the years 1981-2010 from TopoWx. TopoWx was recently completed at the University of Montana. Minimum temperatures are interpolated from climate stations using elevation-based variables and satellite data as predictors of air temperature.

For each 800-kilometer square area in the area-of-interest the daily interpolated minimum temperature was assessed to determine if it was greater than 32 degrees Fahrenheit for each year in the period 1981-2010. The number of days was accumulated for each 800-kilometer square area when that event occurred.  The 30-year annual mean was calculated from the number of frost-free days for all years in the period 1981-2010.

Content Credits:

Degree Days from Temperature

Online map of mean heating degree days

Online map of heating degree days (Web application)

Online map of heating and cooling degree days (Web application)

Image of mean heating degree days map (JPEG)

Print version of mean heating degree days map (PDF)

Mean heating degree days for the years 1981-2010 from TopoWx. The colder the outside air temperature the greater the number of heating degree days and the more energy it takes to heat a building. TopoWx, recently completed at the University of Montana, interpolates temperatures from ground station and satellite data.

The heating degree days calculation used a base temperature of 65 degrees Fahrenheit and the mean daily temperature. The difference between the mean temperature and the base temperature, if positive, results in the number of degree days. The colder the outside air temperature the greater the number of heating degree days and the more energy it takes to heat a building. For each 800-meter square area in the area-of-interest the daily interpolated minimum and maximum temperature from TopoWx were averaged for each day in the period 1981-2010 to create a daily mean temperature product. The degree days were calculated for each day and summed for each year in the period. The 30-year annual mean was calculated from the annual degree days for all years in the period 1981-2010.

Content Credits:

Online map of mean cooling degree days

Online map of cooling degree days (Web application)

Online map of heating and cooling degree days (Web application)

Image of mean cooling degree days map (JPEG)

Print version of mean cooling degree days map (PDF)

Mean cooling degree days for the years 1981-2010 from TopoWx. The warmer the outside air temperature the greater the number of cooling degree days and the more energy it takes to cool a building. TopoWx, recently completed at the University of Montana, interpolates temperatures from ground station and satellite data.

The cooling degree days calculation used a base temperature of 74 degrees Fahrenheit and the mean daily temperature. The difference between the mean temperature and the base temperature, if positive, results in the number of degree days. The warmer the outside air temperature the greater the number of cooling degree days and the more energy it takes to cool a building. For each 800-meter square area in the area-of-interest the daily interpolated minimum and maximum temperature from TopoWx were averaged for each day in the period 1981-2010 to create a daily mean temperature product.  The degree days were calculated for each day and summed for each year in the period. The 30-year annual mean was calculated from the annual degree days for all years in the period 1981-2010.

Content Credits:

Online map of mean number of days over 90 degrees Fahrenheit

Online map of mean number of days over 90°F (Web application)

Online map of heating and cooling degree days (Web application)

Image of mean number of days over 90°F map (JPEG)

Print version of mean number of days over 90°F map (PDF)

Mean number of days over 90 degrees Fahrenheit for the years 1981-2010 from TopoWx. TopoWx was recently completed at the University of Montana. Maximum temperatures are interpolated from climate stations using elevation-based variables and satellite data as predictors of air temperature.

For each 800-kilometer square area in the area-of-interest the daily interpolated maximum temperature was assessed to determine if the temperature exceeded 90 degrees Fahrenheit for each day in each year in the period 1981-2010. The number of days was accumulated for each 800-kilometer square area when that event occurred.  The 30-year annual mean was calculated from the annual number of days over 90 degrees Fahrenheit for all years in the period 1981-2010.

Content Credits:

Online map of mean crop degree days

Online map of mean crop degree days (Web application)

Image of mean crop degree days map (JPEG)

Print version of mean crop degree days map (PDF)

Mean crop degree days when temperatures exceed 32 degrees Fahrenheit for the years 1981-2010 from TopoWx. The warmer the outside air temperature the greater the number of crop degree days. TopoWx, recently completed at the University of Montana, interpolates temperatures from ground station and satellite data.

The crop degree days calculation used a base temperature of 32 degrees Fahrenheit and the mean daily temperature. The base temperature of 32 degrees Fahrenheit is used as a reference temperature in phenology calculations for Montana crops as published by the Montana State University Extension Service (MONTGUIDE MT200103 AG 7/2001). The difference between the mean temperature and the base temperature, if positive, results in the number of degree days. For each 800-meter square area in the area-of-interest the daily interpolated minimum and maximum temperature from TopoWx were averaged for each day in the period 1981 through 2010 to create a daily mean temperature product.  The 30-year annual mean was calculated from the annual crop degrees days for all years in the period 1981-2010.

Content Credits:

Online map of mean date for hard red wheat developement

Online map of mean date for hard red wheat development (Web application)

Image of mean date for hard red wheat leaf development map (JPEG)

Print version of mean date for hard red wheat leaf development map (PDF)

Mean date for hard red wheat leaf development (Stage 1.1) based on degree days of between 336 and 406 with a base temperature of 32 degrees Fahrenheit for the years 1981-2010 from TopoWx. TopoWx, recently completed at the University of Montana, interpolates temperatures from ground station and satellite data.

The degree day calculation used a base temperature of 32 degrees Fahrenheit and the mean daily temperature. The base temperature of 32 degrees Fahrenheit is used as a reference temperature in phenology calculations for Montana crops as published by the Montana State University Extension Service (MONTGUIDE MT200103 AG 7/2001). The difference between the mean temperature and the base temperature, if positive, results in the number of degree days. For each 800-meter square area in the area-of-interest the daily interpolated minimum and maximum temperature from TopoWx were averaged for each day in the period 1981 through 2010 to create a mean temperature product.  The degree days for each 800-meter square area were summed for each year in the period until the total number of degree days was between 336 and 406, which is the threshold for hard red wheat leaf development (Stage 1.1). The Julian day was recorded for each 800-kilometer square area when that event occurred. The 30-year annual mean was calculated from the annual crop degrees days for hard red wheat leaf development (Stage 1.1) for all years in the period 1981-2010.

Content Credits:

Online map of mean date for hard red wheat developement

Online map of mean date for hard red wheat development (Web application)

Image of mean date for hard red wheat maturity map (JPEG)

Print version of mean date for hard red wheat maturity map (PDF)

Mean date for hard red wheat maturity (Stage 8.9) based on degree days of between 2800 and 3029 with a base temperature of 32 degrees Fahrenheit for the years 1981-2010 from TopoWx. TopoWx, recently completed at the University of Montana, interpolates temperatures from ground station and satellite data.

The degree day calculation used a base temperature of 32 degrees Fahrenheit and the mean daily temperature. The base temperature of 32 degrees Fahrenheit is used as a reference temperature in phenology calculations for Montana crops as published by the Montana State University Extension Service (MONTGUIDE MT200103 AG 7/2001). The difference between the mean temperature and the base temperature, if positive, results in the number of degree days. For each 800-meter square area in the area-of-interest the daily interpolated minimum and maximum temperature from TopoWx were averaged for each day in the period 1981 through 2010 to create a daily mean temperature product.  The degree days for each 800-meter square area were summed for each year in the period until the total number of degree days was between 2800 and 3029, which is the threshold for hard red wheat maturity (Stage 8.9). The Julian day was recorded for each 800-kilometer square area when that event occurred. The 30-year annual mean was calculated from the annual crop degrees days for hard red wheat leaf maturity (Stage 8.9) for all years in the period 1981-2010.

Content Credits: