I lived on a neighboring Caribbean island for 18 years. While Mother Nature can always throw you a curve I can tell you that weather on Anguilla and St. Martin during the latter part of June and into early July is usually very nice. Because Anguilla is a relatively flat and arid island it usually gets much less rain than the nearby mountainous island. Because St. Martin is somewhat hilly it will get slightly more rain. As one of the previous poster said, rain on both islands, if it does come, is usually in the form of very brief widely scatter showers lasting minutes rather than hours. It is not unusual for it to sprinkle in one area and be bright, sunny and dry 1/4 mile away. All day rains are rare. For what it is worth, I've seen it rain in my backyard and at the same time be sunny and dry in my front yard.
While it is technically Hurricane Season, the biggest threat of major storms is in the latter part of August through late October. The Caribbean covers a vast area so even if there is a Hurricane in the Caribbean during the time you are visiting the odds are small it will impact Anguilla. You can research the frequency of every hurricane that impacted Anguilla since 1850 at
www.stormcarib.com - on the Home Page click on the "Climatology" link then select "Hits & Misses". On the new page select "Anguilla". If you review the data there you'll find in all that time there have only been 4 hurricanes that impacted Anguilla in July and 0 (zero) in June since 1852. The statistics are essentially the same for St. martin. Pretty good odds, I might say.
When visiting Anguilla or St. Martin at that time of year you can leave your umbrella at home and pack plenty of sunblock, you'll need it. If you do encounter some rain during your visit you have a couple of good options: 1) go swimming as you'll get wet anyway, 2) take shelter under a nearby palm tree until the rain passes or 3) go to the nearest bar and order a pina colada or other frozen cocktail but don't be surprised if the rain stops before the bartender finishes maxing your drink.
