My 5 yo woke up with fever in the middle of the night

It's been pretty hot lately. My 5yo girl is v energetic thru out the day. She wants to play all the time even if it's hot. She is always okay tho.

But I woke up to my husband telling me she feels hot. I got up and check and yep she seemed feverish. Took the temp in the underarm the temp was 99.2. Then took another reading from the mouth, it was 100.3. I gave her panadol. We usually drink very chilled water. We have air conditioned rooms but the whole house isn't air conditioned. Could it be because of heat? Or am I expecting a viral or something? I also have an almost 17 weeks old baby. I'm so worried may Allah help us