Blackleg, caused by Leptosphaeria maculans, inflicts greatest canola yield losses when plants are infected before reaching the six-leaf growth stage. During this period, fungicide applications made more than one week after initial infection provide significantly less protection. The objectives of this study were to characterize the dynamics of L. maculansascospore dispersal and to identify environmental factors associated with this phenomenon. Airborne ascospores concentrations were monitored using Burkard 7-day volumetric samplers between mid-May and mid-July in Langdon, ND in 2017 and 2018. Ascospores were identified and counted under compound microscope. Concentrations > 5 ascospores/m³ of air were considered peaks. Ascospores concentrations peaked during mid to late June in both years when canola plants were at early bud to flowering stage. Logistic regression analysis indicated there was a significant association between ascospore peaks and seven-day moving averages of daily mean relative humidity and soil temperature. In this way, there is a 50% probability that ascospores peaks would occur when the daily mean relative humidity is at 50% and the soil temperature is at 15^oC. These results suggest that a warning-system could be developed; however, additional locations-years are needed to strengthen it before it is deployed.