A method for determining the growing degree units (GDUs) accumulated at a particular farm site throughout the growing season, the amount that such accumulation is above or below the average historical GDU accumulation that occurred at the farm site, and a GDU meter for obtaining and displaying such information. The GDU meter measures and stores the temperatures that occur at a farm site throughout every 24-hour period of the growing season and calculates and stores the accumulated GDUs that impinge on the site year to date. The GDU meter compares the GDUs accumulated year to date (year to date GDUs) to the average GDUs accumulated in previous years at the same site (historical GDUs) and calculates how much the year to date GDUs are above or below the historical GDUs. The GDU meter of the present invention displays year to date GDUs and the amount that it is above or below the historical GDUs. Optionally, the GDU meter of the present invention displays the date, time, and temperature. The GDU meter may be connected to the Internet for transfer of the GDU data contained in the GDU meter to a website accessible to the farmer.