he Delta T is the spread between the wet bulb temperature and the dry bulb temperature (in degrees C). Delta T offers a quick guide to determining acceptable spraying conditions. For example, it is not recommended to apply pesticides when Delta T is above 10 - a range of 2 to 8 is ideal. With the Kestrel 3500 Delta T, the calculation is done for you, accurately and simply. The Kestrel 3500 Delta T incorporates barometric pressure correction in its wet bulb temperature calculation, ensuring accuracy even on low pressure days, at high altitudes, and in the very dry weather when Delta T monitoring is important. No other hand-held weather meter offers this feature with this level of accuracy. Kestrel 3500 Delta Tracker Pocket Weather Tracker 0835DTRegular price: $259.00Sale price: $195.00 Need more information? Please feel free to contact us at 1-800-592-6940 - Ask for Extension 547 or Internet Sales.