Add to cart Digital Thermometer $37.00 Size: N/Aor 4 payments of $9.25 with Afterpay Digital Thermometer The most basic item for a greenhouse is a thermometer. This will allow you to keep an eye on the temperature in the greenhouse. If your greenhouse is large, use several thermometers in different areas. Place a thermometer in the shade near the middle of your greenhouse and monitor the temperature at different times during sunny and cloudy weather. The temperature readings you record will vary depending on the type of plants being grown.