Why Won't My Car Start When It Rains?

Usually the cause of a no start in rain/high humidity conditions is that the spark voltage is arcing to the engine metal rather that to the spark plug because of worn out spark plug wire insulation. You may be able to observe this when the engine is running at night in a dark location when it is wet outside by opening the hood and observing for arcs jumping out from the spark plug wires. The distributor cap could also be cracked which can also short the voltage to ground. So my first suggestion is to replace the spark plug wires and look carefully at the distributor cap for any signs of a crack.

I read the blog about using Wd-40 and it works,just tryed it.Spray the cap and the wires and car starts right up .I have 1996 honda accord.Total cost $1.69

Its either your cap and/or rotor or, your main relay. If you replace those and it does not help, my advice would be to take it to a shop. Otherwise your going to be spending a lot of  money on suggestions.

: P.s in my professional opinion ( I am a master mechanic ) Dielectric grease is a far

Like I was saying Dielectric grease is a far better choice than WD-40

Hey my car does the same thing. Its an 89 volvo 740gl, the reason why mine does it is because there is a leak in one of the plugs on the bottom of my distributor cap and so the oil shoots into the distributor cap. When that happens the oil sucks in the moisture from the rain and causes the sparks to misfire. :)

Spark gap being prevented by moisture in the distributor cap or between the points.

Need to check the rotor cap it might be cracked an letting moister in you can take cap off an put baby power in it to see if is cracked

I own a 1990 honda accord. Lately when it rains it will not start. Right after it clears up the car will start. My mechanic seems to think it is a relay. What else can it be?

All of these answers are fine and dandy but what if I need to use my car like... Now!? Doesn't anyone have a quick fix to dry it out, like something with a hairdryer?

It could be because its to wet or something to do with the engine