Warm weather causes toxic plankton to bloom all over the coast of British Columbia whether a month has an "R" in it or not. If you are not absolutely sure that the shellfish you are about to eat is safe then don’t eat it. Bivalve molluscs like oysters, clams and mussels are all susceptible to red tide. Butter clams are the very worst, retaining toxins for long periods of time. Cooking does not alter the toxicity of these filter feeders in any way.
If you are going to an area where shellfish harvesting might be possible then make it a habit to call the federal government’s online Red Tide advisory. As with so many government services this one too is needlessly confusing. Where appropriate, I have included Fisheries Management Area numbers with each trip description. Armed with that information, navigating the Fisheries and Oceans Canada's online list of Bivalve Shellfish Contamination Closures is much simpler. On the same site there's a slow-loading map detailing closures as well.