Sometimes it just happens this way for no other reason than it can. Stress, angst, feeling unwell, or just the heat. Have you had alcohol recently, sometimes you can have a delayed reaction with alcohol and you will see higher than expected levels for a few days at least that is what sometimes happens with me. If I do see higher numbers, I just eat carnivore (no carbs) until things stabilise.
Just another thought. Are you sure you can trust your test strips with all the heat we have had? I think one of my boxes of test strips or my actual glucose meter is messed up. I have 3 glucose testers (Not greedy really, there are perfectly valid reasons to having 3, used to have 2, one as a backup but inadvertently bought the wrong test strips for one of my devices. It was cheaper to buy a new meter than ditch the multiple boxes of non returnable test strips I had purchased) I generally keep to one for consistency but occasionally will check with one of the others. I did a check with a meter I do not regularly use but have test strips in date to use so I used this tester as a check. Showed up 9.4! Tried once more still results were in the same region, tried with my two other meters, both sets of results came back in the 5s.which is what I would have anticipated. Extremes of temperature can do funny things with test strips. Think I need to check the device with a control solution. Don't know if any of this is helpful but feel for you as it can be so frustrating.