You should start sowing seeds then, where the conditions most conducive to sprouting exist. The seeds will then emerge quickly and evenly. Sowing under unfavorable conditions may cause unevenness and delay the emergence time, exposes some of the sprouted seeds to drying out, makes it easier for birds to eat seeds, etc.. Lawns set up in such an inappropriate period are of lower quality, they require sowing larger amounts of seeds and an increase in maintenance.
The basic factors determining the sowing time are: temperature and humidity of soil and air.
In spring, favorable conditions are usually found in May, often from mid-April. In the second half of May, however, very often high temperatures and no rainfall occur, which can make it very difficult to rise.
Perennial ryegrass sprouts the fastest (rye grass), because it's over 5 – 15 days. The spring period is very favorable for sowing mixtures with a predominance of this species. Other species, like bumblebee, crest, fescue and annual panicle sprout much longer, bo 15 – 21 days, and the rest of the panicles, like a meadow, ordinary and gamekeeper - even longer, bo 20 – 40 days. Sowing seeds of these species in the spring can prove to be very unfavorable, especially if watering cannot be ensured or if the species are components of mixtures with a low ryegrass content (which protects the soil earlier as it rises).