You can request the temperature at any time while mains power is available. When the power fails, the unit goes into sleep mode to save the small internal battery. Because of this, it cannot report temperature continuously during power outages.
We plan a future software update that will allow “smart” temperature monitoring during power outages. You will be able to set how often the unit should wake up to measure the temperature and define thresholds to compare it against. If the temperature goes beyond these thresholds, you will receive a notification. With a reasonable wake-up interval (for example, about once per hour), the unit should be able to monitor temperature for one or two days, possibly longer. We do not yet have a confirmed timeline for this feature, as it is difficult to implement and demand has been low.
In practice, you can still make good decisions if you know the temperature profile of your premises or appliance. For example, if you know how quickly your freezer warms up without power, or how fast your room cools down in winter, you can estimate how long it is safe to wait. If you see that power has not been restored within that time, you know when you must visit the location or take action, even without continuous temperature reporting during an outage.