Sporadic noise, by definition, happens only during some sessions and regardless of what exchange or area code you are calling. There is little you can do about the weather except call out on a sunny day. Radio and tv interference can come from oscillators or transmitters near your modem. Some modems are not properly shielded when manufactured. If you notice problems when a tv is turned on or when a radio transmitter is activated, then you have a shielding problem.
Monitors can also emit significant electro- magnetic fields.
This can also interfere with an improperly shielded modem. Never place a modem on top of a tv or video display monitor. If you suspect this type of interference is causing your problem, try orientating the modem and its cables in different positions to see if that helps. Electronic dimmers also radiate signals. Make sure these are off, or at least at full intensity.