Yep, we hear this all the time. Here’s the physics behind it though. While you may receive some additional cooling from the air blowing over the ice water for a few minutes (think lake effect here), it isn’t going to cause the evaporated air to be so much cooler that you can actually tell a difference without a thermometer. That’s just not how evaporation works – trust us, we are experts. Plus, that ice is going to melt within 30 minutes if it is hot outside. Ultimately, it is up to you whether you put ice in your evaporative cooler. Most likely it won’t hurt anything – we say most likely because theoretically your pump could suck up a piece and seize up. You just have to weigh if you think it is worth a 2°F temperature difference over a 30-minute time period. Personally, we don’t think it’s worth all that work, but maybe it is to you!