Damage caused by hot, dry winds during kernel formation and development of winter wheat ( Triticum aestivum L.) is difficult to assess because under natural field conditions there is never a nonaffected area for direct comparison. An attempt to evaluate damage from hot wind was made by placing a portable wind tunnel, with an auxiliary heat source at the intake, over field-grown winter wheat during the “boot” and the “milk” growth stages. Five 2-h tests were made on wheat plants that had been grown eitherwhere soil water was never limiting or where soil water was always limiting. Air temperature, dew point temperature, and vapor pressure deficit differences from ambient air were determined during each test. Plant water potential (Ψ p) was determined at the beginning and end of each test and soil water content, at the time of the test. At maturity, kernels/head, heads/m 2 of soil surface area, weight/kernel and grain yield were determined. Air temperatures in the tunnel ranged from 4.6 to 8.4°C above ambient air temperature during the five tests. Vapor pressure deficit in the tunnel increased from 0.73 to 2.57 kPa and relative humidity decreased by 4.9 to 14.6% compared with ambient. Reductions in kernels/head, heads/m 2, and kernel weight, compared with the nontreated area ranged from 2.9 to 32.9, 0 to 54.8, and 2.5 to 18.8%, respectively. Maximum grain yield reduction was 65.1%. In two of the tests, grain yield reduction was greatest at 2.5 m past the end of the tunnel. Reduction measured at that location probably more realistically reflects expected reductions than those measured within the tunnel.