Earliest I have found them in NE KS (basically state line north of Topeka) is first week in April (2 years ago). One year I didn't find any until about the first of May (last year). Normally its around the middle of April. This year will be later than normal unless we get an extreme heat wave. The soil temp needs to remain in the 50's for about a week and they'll start popping. Once the soil temps stay in the 70's they quit. Soil temp this morning was 38. Soil temps fluctuate much more than water temps that could make it to the 50's with a good week of weather. So that means we would need about 2 weeks of good weather to start seeing shrooms. I'm guessing around the 21st of April here. Further south will be earlier. Some years I hear of people finding them south of Topeka 2 weeks before I do.