The microclimate of the field vole (Microtus agrestis) was measured in rough grassland in SW Scotland from February'April 1992. Measurements represented conditions experienced by voles when foraging. Air temperature in the grass tunnels used by voles was only 0.3°C greater than air temperature above the vegetation. On average, the change in temperature in grass tunnels and at feeding stations used by voles matched the diurnal increase in air temperature. However, snow cover was found to insulate vole habitat from large changes in air temperature. The grassland provided considerable shading from solar radiation and shelter from wind. Solar radiation and wind speed at the surface were closely coupled with conditions above the ground surface due to the short height of grassland at this season of the year. Although the winter temperatures experienced by field voles are well below their thermoneutral zone of metabolism, their sheltered microclimate means that they can remain active in wet and windy weather when predators may be less able to detect them.