Changes in fire regimes can raise wildland fire risk due to increases in frequency, size, and intensity of wildland fires. They may also result in a longer fire season, the portion of the year when most ignitions are observed. A method is proposed to investigate spatial trends in the timings of the start and end of the fire season across Ontario between 1960 – 2022. Using interpolation on the times and locations of historical fires, an algorithm is introduced to create smooth spatial surfaces of fire season start/end dates across our study region, allowing us to test for evidence of monotonic trends. We consider changes to the proportions of the year before, during, and after the fire season, while also contrasting trends based on all ignitions, only human-caused ignitions, or only lightning-caused ignitions. In Northwestern Ontario, we find evidence of human-caused ignitions starting earlier and lightning-caused ignitions continuing later, resulting in longer fire seasons.