You should not apply Termidor SC if it is going to rain the same day. It is best to wait until you have a few days of no rain in the forecast. Termidor SC is made to bond to the soil but it needs time to "set" and bond to hold up against a rain event.
If kept out of heat and sunlight the shelf life of Termidor SC is 3-5 years.
The only temperature that effects Termidor SC is when it is below freezing. Termidor SC should not be applied if the ground is below freezing, or it will not take hold
If you are applying Termidor SC you want to make sure there is not going to be rain for at least 24 hours after application. If you know it is going to rain within that time frame, you should wait until the rain is passed and will be sunny and dry for a day or two