False temp?

Woke up around 2-2:30am today and took my temp and it was 97.66. I fell back to sleep. Woke up around 5:30 due to my alarm, and took my temp again and this time it was 98.24. Pretty big jump from the 2am temp so I'm just wondering if it's accurate or not? I’m between 10-12 DPO today.