A planet generally with an earthlike climate, although slightly wetter and warmer as a general rule, with a little more oxygen in the atmosphere, but habitable by unmodified humans. Still has equatorial and polar variation.
Planet has constant winds.
Stable enough long enough to have evolved a sapient species with an adequate level of technology to completely contain expansion of a refugee colony of humans of mildly (but nonspecified) post-modern tech.
What good reasons could there be for this planet to have, multiple times per year, on either a completely or semi predictable schedule, extended periods of hot, dry, dusty winds that cause native life to generally close up and hide? This does NOT have to be planetwide, but does have to be prevalent enough that the sapient species and most others have evolved strongly adapted to it. By extended, I mean at least long enough for a caterpillar like metamorphasis of several hundred pound creatures to occur.
Solar year can be significantly longer than earth's, and the dry winds don't necessarily have to be connected to any other function of regular seasonality, ie not necessarily during a 'summer' or whatever. They should be predictable by at least several days however.
Edits: There is no need for the planet to be based in any particular kind of orbit as long as it meets the rules. The setting is more science fantasy than hard science fiction, so answers don't have to be super strict on hard science, as long as they make general sense.
The best answer will incorporate either an irregular cycle, or a cycle that is regular on such a long timeline that it is difficult to perceive, or a regular cycle with potential for intermittent irregularity. These periods would typically occur no less than 2-3 times in a solar year. The hot dry spells would not be so extreme as to be immediately dangerous to most creatures, but would be a severe stress over time if not protected/sheltered from in some way (ie walking around the Sahara unprepared)