The impact of a manually operated energy curtain on the recorded nighttime inside air and soil temperatures, relative humidity (RH), and daily light integrals during early-season high tunnel tomato (Lycopersicon esculentum) production in central and southern New Jersey were examined. Environmental data (air and soil temperatures, RH, and photosynthetically active radiation) were collected from late March through mid-May at two New Jersey locations for the 2004 and 2005 growing seasons. The continued impact of the early use of an energy curtain was further evaluated by collecting light, temperature, and marketable fruit yield data for the remainder of both growing seasons for one of the two experimental sites. Results showed that although the use of the curtain modestly increased early season nighttime inside air and soil temperatures and RH, the curtain reduced accumulated light integral during the first 7 weeks after transplanting and resulted in a marginal early yield increase. The main benefit of the energy curtain occurred on cold nights when an early season crop might otherwise be exposed to potentially damaging low temperatures.