Mayfly Genus Baetis (Blue-Winged Olives) hatch throughout the year, in the spring and fall thy do tend to be smaller than in the early spring and fall. There are in fact dozens of different types in our province. I have often chased pods of Rainbows and browns during these hatch cycles. You also have to look at stages of nymphs that are pre-emergers for a complete cross section in your box. Often anglers look for that one magic fly that works all year instead of looking at what is on the water at different times of year and differnt nymphal stages(an insect screen can be your best friend to determine size and color). Here are a few that work for me throughout the year. Some are original others specific to well know patterns. I tend to bend my patterns to what I see on the water.
Red Headed Step Child mentioned here in #16 and #18
My Doc's BWO (personal favorite) in Size #20
Suspended BWO Nymph #18 - #20. The large tail is pre-shuck
Bars Emerger is a good one fished in a Leisenring Lift manner. Tie it in Green and brown.
Doc's Gilled Baetis Nymph
Hope this helps a bit in chasing the BWO hatches. keep up your social distancing and keep safe and may wee all meet at some time on sparkling waters.