not lagging in diligence, fervent in spirit, serving the Lord;"
Romans 12:10-11 (NKJV)
Temperatures in the Summertime can get very high, more so in some places than in others. Some places I have been, like Oklahoma and Texas, can have some very hot temperatures during the Summer months, this is why air conditioning is so nice. The temperature can be extremely hot outside, but with air conditioning things can be very cool inside. You could pass by a house or some building during the hot weather and although it does not look so from the outside, where it is hot, it is very cool inside the building.
In the same way, Christians can look one way on the outside but have something different going in inside of them. Some believers may jump, shout, and do a lot of great things in church, but that is not who they really are. Too many Christians are "hot" when it comes to an exciting service or a special meeting, but unless something outside of them "heats them up" they are cool and lack any zeal to do anything God might be calling them too. They may be hot on the outside but they are cool on the inside.
Romans 12:11 says to be "fervent" in spirit; this word literally means to be hot. We need to have a fervent, "hot", desire within us to spend time with God and His Word more than just when a special meeting takes place. We should have a zeal to reach the lost and take the Gospel around the world more than just when we hear a touching story from a missionary. We should have an interest in helping others more than just when it directly benefits us. By staying full of God's Word and following the direction of the Holy Spirit we can be fervent, hot, inside and outside spiritually all year long.