The meteorological sensors gave further information about the atmosphere. They found patterns of diurnal and longer-term pressure and temperature fluctuations. The temperature reached its maximum of 263 kelvins (–10 degrees Celsius) every day at 2 p.m. local solar time, and its minimum of 197 kelvins (–76 degrees Celsius) just before sunrise. The pressure minimum of just under 6.7 millibars (roughly 0.67 percent of pressure at sea level on Earth) was reached on sol 20, the 20th martian day after landing. On Mars, the air pressure varies with the seasons. During winter, it is so cold that 20 to 30 percent of the entire atmosphere freezes out at the pole, forming a huge pile of solid carbon dioxide. The pressure minimum seen by Pathfinder indicates that the atmosphere was at its thinnest, and the south polar cap its largest, on sol 20.

Morning temperatures fluctuated abruptly with time and height; the sensors positioned 0.25, 0.5, and 1 meter above the spacecraft took different readings. If you were standing on Mars, your nose would be at least 20 degrees Celsius colder than your feet. This suggests that cold morning air is warmed by the surface and rises in small eddies, or whirlpools; this is very different from what happens on Earth. Afternoon temperatures, after the atmosphere has warmed, do not show the same variations. In the early afternoon, dust devils repeatedly swept across the lander. They showed up as sharp, short-lived pressure changes and were probably similar to events detected by the Viking landers and orbiters; they may be an important mechanism for raising dust into the martian atmosphere. The prevailing winds were light (less than 10 meters per second, or 36 kilometers per hour) and variable.