We examined the influence of a moderately severe wildfire on the thermal patterns in three small streams in central Idaho, USA, for an 11-month period beginning ten months after the fire. Two streams in unburned catchments served as reference sites. No differences were observed between the burned and reference streams in daily minimum temperatures or in the general thermal conditions during winter. During late summer and early autumn, when solar radiation was greatest, the burned streams displayed warmer temperatures than did the reference streams. During non-winter months, the burned streams experienced diel ranges in water temperature 2-3 x greater than those of the reference streams. Despite these differences, the number of degree-days accumulated among the streams was similar. In general, the wildfire altered the thermal stability of the burned streams, relative to the reference streams. Return to a pre-fire condition is expected to occur as riparian vegetation (shading) recovers along the burned streams.