@Benjamin, if you've been out to the desert in the last few days (since the rains lashed the country), then chances are there's been a ton of sticky sand & mud stuck to the underside of your car. My recommendation, and as @Looper has suggested earlier, just get it cleaned from time to time.
After driving in muddy conditions, getting the undercarriage cleaned is even more crucial. I learned this the hard way because while I would take my car for "body washes" in the first 10 or 12 drives, they would never wash the undercarriage. 15 drives later, when I finally did an undercarriage wash, the team at the car wash had to use a ton of elbow grease & kerosene to loosen the sand & mud that had caked onto the undercarriage components. Hence, just like you should clean out your air filter after 3 to 4 drives, make it a point to have your undercarriage pressure washed after every 4 to 5 drives.