Area Long Term Weather forecast/history

Hi,

Any suggestions for getting a long term historically based weather
forecast several months ahead?

I am planning a trip to the USA with lots of flying. I would like to
select the area to fly in taking into account the likely weather,
amongst other factors. How many days if any am I likely to be IFR or
marginal VFR? How likely am I to be diverting and grounded part way
on long cross countries?

Likely areas are Florida and SC, NY/NJ/PA, TX.

200hr PPL. Renting whatever I can find, although I normally fly a
Piper Lance at home