DS

It depends on what depth you want to know about. There's a site here in Georgia that lists soil temperatures at 2" (I assume that's the one to consider for sowing seeds), 4" (first root development?) and 8". For instance, today the soil temp at 2" is listed as 57.2, 4" is 56.6, and 8" is 55.7.

Who knows the best time to test it! It may not change that much during the day.

I guess but various books like to list soil temps for optimal planting. Those temps can vary a lot by time of day. I find it hard to believe that there isn't some standard.

I can tell you how I do mine if that helps. Old wall thermometer - the kind with the red liquid bulb in the bottom of a tube glued to a simple backboard and calibrated on one side in F and the other side in C degrees. I just stick it in the ground to the desired level and wait several minutes then pull it out and check it - note the reading. I measure early in the morning as it will most likely be warmer later in the day.

It is soil at the germination level that is relevant and that's all you have to worry about. So note the recommended planting depth and check to that level or just a bit deeper. Most all seeds are planted to germinate at no more than 1-2". For planting tomatoes and peppers I push it in 6".

If the temp holds at that level for 2 days in a row, I plant. It isn't fool-proof but it works for me. ;)

Linked a tech 'how-to' below. Note they recommend checking it 2x a day.

Hope this helps.

Dave

Here is a link that might be useful: How to measure soil temps

I have a couple of quick-read meat thermometers I use for cooking. I have a couple more, (one for each refrigerator) to keep a watch on my beer temperature. When I wonder what my soil temperature is, I take one out of a refrigerator and stick it in the ground to any depth I want, up to about 6".

Tom

I have always used cooking thermometer as it will give me a quick temperature at two to four inches.

Down 4 inches I find only slight temperature change from night to day. At 2 inches there is some. The top inch or so is all that has drastic swings with changing air temps and sunlight. Might be different in areas with more intense sun, but not in my garden. 42 degrees N latitude. So for seeds and transplants going in a few inches deep, I measure temp whenever it is convenient. I also use a meat or oven thermometer (round dial with a 6 inch point coming out the back) It looks just like the soil ones I've seen in catalogs but was cheaper and didn't need to be ordered.

I believe it was Gene Logsdon that said to measure at high noon.

Sue