I've done many outdoor weddings where the couple did not have a back-up plan in case it rained. I can't stress enough the importance of planning for the unexpected, even in June. This is Northern California, and every year I hear someone say, "What strange weather we're having this year." By now, I'm used to having strange weather and it no longer surprises me when it rains in the summer and when we have heat waves in the winter.
A useful website for this is www.intellicast.com. When you access this website, enter the zip code or the city, state AND country. The current weather will come up for your city. You will see a blue menu bar with the following options: Weather Report, interactive Weather Map, Extended Forecast, etc. Select "Historic Averages." This will give you the monthly and daily temperature and precipitation numbers for your city.
You may use that website not only for your wedding day, but to look up the weather in the city where you will go on your honeymoon. If you find that you will be going somewhere during monsoon season, you may have time to find a different honeymoon destination.
If you wish to plan your wedding ceremony or wedding reception around sunset times or wish to know how much daylight there will be, I recommend looking it up at www.sunrisesunset.com. Just select the citiy and month. When you select the "Make Calendar" button, you will see a calendar for the month you selected at the city of your choice.