• global warming;
  • mountain environments;
  • nighttime temperature change

[1] While the upward trend in global mean temperature has been intensively studied, some regional temperature trends are less well known. We document secular temperature changes in the Hawaiian Islands for the past ∼85 years based on an index of 21 stations. Results show a relatively rapid rise in surface temperature in the last ∼30 years, with stronger warming at the higher elevations. The bulk of the increase in mean temperature is related to a much larger increase in minimum temperatures compared to the maximum—a net warming about 3 times as large—resulting in a reduction of the diurnal range. For much of the period of record analyzed here, surface temperature in Hawai‘i has varied coherently with changes in the Pacific Decadal Oscillation (PDO). However, in recent decades, the secular warming has begun to predominate, such that despite the recent cooling associated with the PDO, surface temperatures in Hawai‘i have remained elevated. The greater warming trend at the higher elevations may have significant ecological impacts.