Lucky you!!! We had wanted to go camping last week but due to both of being ill, it didn't happen. We have a 3-day weekend next week and if the weather doesn't get too hot, we're going to get out one more time before "Super-Summer" sets in. Like you, we're "heat-wimps" as well

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Took a look at McKinney Falls a number of years ago. It sure is a nice park with a lot of nice sites. Have been wanting to get back there for some camping but it just hasn't happened yet.
Kind of surprised about the swimming restriction. Would have thought all the rain would have washed out all the pollutents (sp?). I'm sure the rangers know what's best as they test the water daily, from what I understand.
You mentioned that your thinking about a trip to Blanco for October. You won't go far wrong with that choice. Here's a link to a review I did of that park a couple of years ago. Hope it helps.
http://www.wildtexas.com/talk/showthread.php?t=813
Glad you had a great trip and hope you have many more.
Happy Camping!
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Turn Key, DW & Tilly, The Camping Boston Terrier
'03 Chevy 2500HD, 4X4, X-Cab, Long Bed
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Twin Kayaks, "The Ride" by Wilderness Systems
North Central Texas, Where The West Begins!