As of mid-May there are two zones of extreme drought conditions in the state of Colorado. With moderate drought over much of southern Colorado.
Drought conditions this severe can increase fire danger on a daily basis, but where a fire occur brings highly variable conditions for fire crews.
Let's compare grass fires in the plains versus forest fires in the mountains.
Grasses in general are quick drying. From spring green up, they can completely dry out within days or weeks depending on weather. Forest foliage is a bit more complex and much slower to dry out. They will dry after snowpack melts and spring green up, taking several weeks or even months to completely dry.
Grasses burn very quickly, and can spread tens of thousands of acres in the span of an afternoon. Generally, they last hours or days. Forest fires burn much slower, consuming smaller acreage per day, yet can last weeks or months.
In the grasslands of Colorado, winds will drive the speed and direction of wildfires. In the mountains, the terrain can effect the spread of forest fires more so than wind.
Wildfires can technically happen any time of year. They "typical" beginning of grass fire season is in the spring after the initial greening of plants. Because of the longevity of snowpack and longer time for fuels to dry, forest fire season typically starts in summer.