on the Big Island
Having spent the last quarter century as a hang glider pilot I think I have some grasp of weather decisions. If you make a bad weather decision in hang gliding you may either be scared completely out of the sport or have some chance of being maimed or killed.
In kayaking it may not often be so crucial but it could be. There have been people blown far off the island. One guy was testing out a kayak with a sail (luckily with a cell phone onboard). When they finally found him he was 120 miles off shore still with his sail up which wasn't in the least bit helping him move back toward the Big Island.
In another instance a guy off Molokai broke a paddle and was picked up 20 miles off Oahu heading out to sea.
Things happen, there are no guarantees in life but with a bit of local knowledge gained about possible hazards it might end up being someone else praying for that solitary ship to spot them in an endless sea.
The best advice I could give would be to either know a bit about the area you intend to paddle, or go with someone who does and hopefully you can gain some insight into the area. Know whether you've got cell service in the area you intend to paddle and carry a cell phone in a drybag anytime cell service is available.
Here are some weather/surf websites that I use to make my decisions on whether to Go or Abort my intended trips.
Swell Watch Best for localized Surf conditions
There are some areas of the Big Island that are more safe than others like Hilo Bay, Keahou Bay and Kealakekua Bays on the safer side and on the more dangerous end of the spectrum Upolu Point, South Point or Mahukona would be less than optimal to have your first (or last) kayaking experience.
So Hilo Bay and Kona/South Kona area are generally pretty safe barring hurricane or thunderstorm warnings which one would hope you'll be paying attention to and there are other great places to kayak on this island that only require you understand a bit about Big Island weather and stay alert as you're paddling.
The first thing to understand is the normal trade winds which blow from the NorthEast or Easterly direction. The local news will forcast them every morning and evening or you can call a weather number to get the Big Island or NOAA forcast.
Those NorthEasterly winds are why the Hilo or windward coasts are less traveled by most kayakers, that and the long stretches of unlandable coastline. That wind direction also usually protects many sites on the west side of the island until the trades get higher, overpowering the coastal breezes on the west side until some normally serene west coast sites do become dangerous.
10-20mph trades is a pretty average forecast but even then you can expect the winds to double or triple in strength out in the Ali nui haha Channel (where you definitely don't want to end up) as they get compressed between the Mauna Kea and Haleakala Mountains.
Anything below that average is usually going to give you better than average paddling conditions islandwide especially in the normally windier parts of the island. Be especially alert when the trades are forecast at higher than average velocities. 10-25 or 15-30 can be real trouble in areas like Puako, South Kohala or Kiholo which are normally beautiful but become wicked offshore winds (sometimes doubling what was forecast) when those heavier trades kick in.
Regardless of the forecast be extremely wary if you're going to be paddling up in the north Kohala area or anywhere close to MahuKona, or South Point as the accellerated trades venturi down off the mountain to feed the windy channel. People do venture out in these areas but it's usually a knowledgeable person paddling in the morning before the winds pick up and if he's smart he's got vhf radion (or locator beacon), water and sinalling device.