Historical patterns of suitability may provide important indicators of potential Karnal bunt disease occurrence. For example, assuming sufficient inoculum is present, a location that has continuous suitable weather can reasonably be assumed to be more likely to harbor Karnal bunt disease than locations where suitable weather does not occur or is rare. To explore climatological suitability we examined daily weather records from 1990 to 2001. We used more than 9000 weather stations to characterize climate across the continental United States. We examined individual years and explored correspondence between known "outbreaks" (a true outbreak has never been observed, field incidence levels have been barely detectable and always very low and very limited geographically) and suitable conditions for specific years. We also developed maps that show for sub-county regions, how many years out of the past decade have 'experienced' suitable conditions. Whereas, we used published literature to derive what weather parameters indicated suitability, our approach can be modified easily as we have developed the necessary databases and statistical scripts to make modifications to the assumptions straightforward. The results of our study show that based on the model used, most of the United States has not experienced suitable weather conditions during the past decade. Our results also show that actual detections of Karnal bunt disease in the field during specific years do correspond with suitability as characterized by the model.