Step 1: Acquire daily high  and low air temperatures from weather station near the area in question. These temps should go back 6 weeks before fall picking begins. For those in the states, there are many sources, online. (Weather links below.)

Step 2: Calculate daily average by adding high and low, then divide by 2. Do this for each day . (Data sheet right)

Step 3: For clay soils, calculate 3 day average by adding 3 consecutive daily averages, divide by 3. Move to the next day, add that day and the previous 2 days, and divide by 3. Do this for every day.
Step 3: For pumice soils, calculate 7 day average by adding 7 consecutive daily averages, divide by 7. Move to the next day, add that day and the previous 6 days, and divide by 7. Do this for every day.
Step 3: If area fruiting is deep, 4" or more, use 7 day average. Regardless of soil type.

Step 4: Plot these temperatures on chart. ( Use a sheet of graph paper)

Step 5: Examine chart to detect formation pattern. Characteristics will be similar to charts on Fruit Formation Page. Patterns begin with a low, followed by warming, ending with a lower temperature than beginning low. Period between, formation. Good patterns stay within a 4 F to 12 F degree rise above formation beginning low. Too low, few form. Too high, mushrooms will form as temps rise, then burn up. In all data examined, 9 F to 10 F degree, ideal. Duration of pattern, should be a minimum of 3 days, maximum length of pattern not established. Mushrooms have been known to slowly grow after 30 to 35 days, before heat bubble ends.  Flushes occur after formation ending low. (end of heat bubble), Usually 2 to 3 days after, depending on temperatures. Refer to Fruit Growth.

Explanation of "Range"

Soils must be cool enough, but not too cold, for formation to be possible. Patterns which occur in summer, starting at 90 F degree and peaking at 100 won't form matsutake. The same is true for the cold end. Patterns beginning at 0 F and peaking at 10, won't form. Ranges are individual to temperature source. For those who have past weather, ranges can be established immediately. Examine data for past years to determine highest pattern producing, and lowest. Any pattern between will form.

If you don't have any idea, most ranges begin below 60 F and above 40 F. This is very general, but ranges are largely dependent on area in question. If your picking areas are at 8000' down to sea level. your range could be 20 degree wide. No ranges have been known to be less than 12 degree wide. No season recorded has ever missed having at least one pattern, within its range, most have 2 to 3.