Watsonville, California's near coast climate makes for a great place to visit and live. With daytime high temperatures seldom above 74 degrees any time of year, and lows hardly lower than 38 degrees on even the coldest winter night, this is the kind of place ideal for growing crops.
For visitors, Watsonville in the less publicized destination shadowed by Monterey to the south and Santa Cruz to the north. But don't let the weather be a factor stopping you from visiting.
The average warmest month is September where you'll find daytime highs around 74-75 degrees, and virtually no rain. Visiting during the months of May through September offer your best chance of "no rain" and sunny skies, while the months of November through March are going to provide good chances that there will be days with rain. Those five months get the bulk of the rainfall for the year, receiving around 20 inches. Take a jacket or raincoat, though it's unlikely that you'll see snow and will ever need a pair of winter boots.
The hottest day on record in Watsonville was recorded in 1987 when the daytime temp reach 106 degrees in October. Most homes don't have air-conditioning, as they rarely need it. However, do take clothes that allow you to dress in layers from light to sweaters and jackets.