You know you can turn on a HomeKit accessory by talking to Siri, but do you know you can turn devices on or off just as easily in the future? Here's how to set impromptu schedules for your HomeKit accessories using Siri commands — and why you might want to. For Temporary Schedules Apple's Home app lets you automate when your HomeKit-compatible lights, heaters, fans, etc. turn on and off. But that's for schedules you follow every day. Using it turns out to be too cumbersome for something you only want to do once. Suppose you are a little cold and turn on a heater. But you want to make sure you don't forget to turn it off so the heater doesn't explode all day and end up with an annoying electric bill. You can tell Siri to turn off the heating in 30 minutes (as long as it can be controlled by HomeKit, of course). Or you can set it to turn off at a specific time, such as 2:30 p.m. Schedule HomeKit accessories with voice commands. The voice commands to set impromptu schedules for your HomeKit accessories are intuitive. Most of the time, it's about knowing you can do this. For example, you can say, "Hey Siri, turn on the living room lights in 15 minutes." This can apply to individual accessories or an entire room. Or you can of course also indicate that accessories/rooms should be switched off. Siri can even create an all-day schedule. You can stack verbal commands in such a way that, for example, a light comes on in the afternoon, off at 2:00 PM and back on at 5:00 PM. If you really want to stretch, you can give commands several days in advance. For example, you can say, “Hey Siri, turn on the kitchen lights at 8 a.m. next Tuesday.” Know the Limitations Unfortunately, one thing I consider to be a useful command is not currently supported. Siri can't handle something like "Lamp on for 15 minutes". If you try, Siri will turn on the accessory within 15 minutes - the opposite of what you want. The order should be split into two commands: "Hey Siri, turn on lamp", pause and then "Hey Siri, turn off lamp in 15 minutes". Tell Siri to turn off a light within 2 minutes and it will do it. Order him to turn on a light for 20 minutes and he does the opposite. Screenshots: Ed Hardy/Cult of MacAnother downside: You can't pre-schedule a change to your HomeKit thermostat using Siri. My testing also didn't show a way to use Siri to set up music or podcasts to play at some point in the future. But the biggest limitation with all of this is that there doesn't seem to be a way to view or edit the HomeKit changes set through Siri. If you use verbal commands to create a temporary schedule, it will be executed. I can't find a way to change an existing Siri command - or even see what's set up. So don't tell your naughty kid about this trick. It can set every light in the house, but it has to come on at 4 in the morning, and you can't know it until you wake up. Just to be clear, don't overuse it: this isn't your only option for your HomeKit accessories. As mentioned before, Apple's Home application provides a complete event scheduling system on your HomeKit accessories. Verbal Siri commands simply add flexibility to temporary changes. If you find yourself giving the same Siri command at the same time every day, consider automating this via the Home app. Unless you just really enjoy talking to your smart home.