Is my Raspberry Pi overheating?

Recently I am getting annoying misbehaviors on my Raspberry Pi.

This Raspberry Pi is NOT the one I used for network tests in my previous posts (Wi-Fi AP hosting is NOT stable on my Raspberry Pi and Hosting a Wi-Fi access point on Debian with Edimax EW-7811Un [Realtek RTL8188CUS]). This is the one I am using for my project. I need to work outdoors with this Raspberry Pi powered on a USB power bank (a.k.a battery pack), so it is pretty tricky to know what the problem exactly is.

Fortunately, with a Bluetooth serial interface, I am able to have my Raspberry Pi talk to a Bluetooth terminal application on my Android phone. Now I plan to figure out if the problem is caused by overheating. Before this post, I have already tried troubleshooting with these possible causes:

1. Too much data being generated and processed by my program.
2. Too much data flowing through the on-board database.

I once thought 1 was the cause. Solving 1 actually gave me pretty many peaceful days with my Raspberry Pi. However, I just found that the problem was not completely solved. I doubt if the temperature is causing these troubles because I personally feel that the problem occurred more frequently in hot days.

I plan to let my Raspberry Pi report its chip temperature(s). Here's what I am going to do with it tomorrow:

http://raspberrypi.stackexchange.com/questions/8689/how-do-i-display-the-temperature-from-the-internal-sensor-on-a-html-page

Since on-board temperature is a pretty commonly asked question for Raspberry Pi, I will not copy and paste the solution to my post. I am not going to do any HTML work either. It is just that the solution was also given in Python.

I like Raspberry Pi Stack Exchange now, however it doesn't seem to have enough active users.
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Updated on July 23

I implemented the CPU temperature monitoring functionality yesterday, and did some outdoor tests. However it was much cooler yesterday than it was on Wednesday. I didn't notice any abnormal behavior on my Pi. When that Raspberry Pi ran indoors with a room temperature of 18 Celsius, the CPU temperature was 40. When it ran outdoors with an estimated air temperature of 28 Celsius, the CPU temperature was 50.

Probably next time when it gets hot enough outdoors, I can testify my assumption.