https://en.wikipedia.org/...nta_Rosa,_California and scroll to climate.

Summer heat waves aren't uncommon in Northern California so I'd prepare for heat.

I've been to that area in late July early August a number of times. Generally expect cooler mornings, often with fog, and hotter midday/afternoon temps. Afternoon winds could be a huge factor.

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Next races on the schedule: none at the moment

I raced the half this July and the temps were higher than average (high 90's) and I struggled on the run because of it. I would definitely prepare for hot conditions.

Our average high temperature at the end of July is 84 degree's with low humidity. Mornings are usually in the 50's (often with marine layer / high fog) and low / no wind until mid-day where it is typically light. Typically our high temperatures last for a short period of time and we begin cooling off in late afternoon with a coastal influence breeze picking up. (plus the run course has a significant amount of shade) The tricky part is evenings can get quite cool so be prepared for that.

All that said, it is summer and there is always a chance for a hot day.

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Dave Latourette
http://www.TTENation.com

In July, the swim will likely be wetsuit legal, but usually right near the limit (~74-76F).

Dave, whats the average/typical weather like for the area for the new October date? What about water temp at the lake?
Thanks!

October is about the same as May temps wise. Perhaps a bit warmer, but rain is more likely.

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Next races on the schedule: none at the moment

Thanks! I have never raced in May, just always did the old Vineman in July. I imagine the run weather could be perfect, but if i recall correctly i remember seeing pics of some pros wearing vests or gloves on the bike one year in may? so i assume a fairly chilly swim and start of the bike? i know california fall weather can range from pretty cold to pretty hot, but just looking for some generalizations.
thanks!

Expect some low 50s in the morning and the highs in the 70s to mid 80s during the day. The water in the lake should be very comfortable - I'd expect 65 degrees give or take Fog can be a major factor though.

The thing is that once you get on the bike you go on a pretty fast descent in a shaded area, and it gets cold there for sure. After the first aid station you will probably want to lose any additional layers.

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Next races on the schedule: none at the moment

Can def be chilly in the morning and almost guaranteed to be a warm afternoon. Fog more common in summer imo. I feel like fall is great weather here and way better than summer.
The other thing to consider is the possibility of poor air quality, we have had some pretty rough fire seasons in past years.

Yes, I agree it should be similar to May dates from the recent past - generally a pretty good condition for a tri. You have to be ready for a range of temps. It's possible you can have a morning in the low 40s, and that's where the jackets/vests/gloves come in handy for the early part of the bike. That said, you can have a scorching hot day in October, into the 90s mid afternoon. I don't have any first hand knowledge of the lake temp that time of year, but I'd think not as cold as May, so yeah, probably decent wetsuit temps in the upper 60s.

High Temps will average mid 70's (74/75) ... Mornings will be cool, i'd expect high 40's to low 50's BUT we start to see some very chilly mornings that time fo year. Water temp will be a bit dependent on weather trend BUT a wetsuit swim and on average we'd see water temps in the upper side of 60's (but the cove is warmer than the open body)

Hope that helps ... it is actually a beautiful time of year!

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Dave Latourette
http://www.TTENation.com