5 mm wetsuit for cold and warm water?

I'm thinking of getting a 5mm wetsuit for the tropics and then using it in the United states and Canada where the water is colder. Is that a good idea? My thought was to but a farmer John 7 mm with a hood on top if the water gets really cold. Therefore I have the following questions:

1) will a 5mm wetsuit be to warm for warm water - I tend to get cold easily

2) Down to what temperature is a 5mm comfortable for most people?

3) Down to what temperature would a 5 mm + 7mm farmer john + hood be comfortable?

I'm a warm water wuss, to the point of ALWAYS wearing a beanie, and I'll generally avoid 5mm wetsuit for water warmer than 82F or so. My usual transition from a 5mm to a 3/2 is when the water gets up to 78 or 79F. You could always go around with the suit partially unzipped, but you can get a good 3/2 mm suit for $100 or less.

As you probably know, the downside to wearing extra neoprene is that you need to wear more lead, and you have more buoyancy change with depth. This downside becomes less important as you get more experience and buoyancy control becomes more and more automatic.

Being a true warm water wuss that firmly believes in taking full advantage of the thermal insulating properties of a 1/5mm thick airplane ticket, I'll let others chime in with info on minimum acceptable temps.

5mm you tend to get cold i would say here you would freeze nicly... i like a 7mm suit in canada... but i dont get cold easyly and retain heat like no tomorrow..

I wear a 5/4 Pinnacle wetsuit and I'm in Southern Okinawa. The water temp here is 20-22 degrees Celcius this time of year. The 5/4 is perfect...if I wear a hood. Much colder than that and I'd wish I had a 5 mil farmer john or a 7 mil wetsuit.

Come summer, when the water is about 82 degrees Farenheit, I'll change to a 3 mil or just a really thin 1.5 mil suit.

I have been using a 5/4 suit for a couple of years and I find it to be a fairly versatile suit. My first 20 dives using the suit were in 80-83 F water and I did get a bit warm, but breaking the neck seal and letting in some water helped cool me off. After that, the suit started to compress and I was not getting overheated anymore. I now have a couple hundred dives on the suit and it works great for me from 75 to 84 F.

As someone who gets chilled fairly easy, I think a 5 mm is the perfect compromise for someone who travels light and needs one suit to handle a variety of temps. In really warm water I leave the back zip open to cool off, and below 75 F add a hood.

i wouldn't recommend a 5mm for cold water, you will get too worm with that. you might wanna get 3mm for warm watter, and maybe a 5 or 7mm full wetsuit to go over the 3mm when it gets really cold, that i think is the best way to go...

so here is how it works

for warm water: 3mm full.
for less than warm watter: 7mm full.
for really cold watter: 3mm with the 7mm on top.

what you need to get:

~7mm full wetsuit.
~3mm full wetsuit.
~a comfortable hood to go with the wetsuits (you might have to buy two different thicknesses for warm and cold watter)

that is my recommendation, hope it was helpful.