Does the temperature rise or fall when it rains?

Of course, the temperature will drop when it rains.

However, the air on the ground will be heated first, and the air pressure on the ground will be reduced.

This will cause the wind to blow from high pressure to low pressure area, often bringing rain clouds. The temperature will naturally drop after the rain. This is a natural adjustment. You feel absolutely right, but the temperature will be higher than usual a few days or some time before it rains.