Full sun is important, even though high temperatures will have to be managed. To aid in natural ventilation, orient the tunnel so that prevailing breezes will blow through the tunnel from side to side. Temperature Management Excessively high temperatures can be very detrimental to tomatoes when they are in blossom. Attempt to keep the inside temperature below 90 degrees F, which might be difficult on some days. Roll the sides up the first thing each morning to control temperature and to flush out the humidity.
Low temperatures can be serious threat to early planted crops inside a tunnel.
Consequently, do not plant more than about 2 to 3 weeks earlier in a tunnel than outdoors. Otherwise, supplemental heat might be required. Even so, a standby propane unit is advisable just in case. Other Management Practices Water. Ample water is needed for the general growth of the plants and to prevent blossom-end rot in tomatoes.