Pick a less strenuous route. Maybe cut back on the number of miles you plan to cover
Plan a route that is in forested land, that follows a stream, or has stream crossings. The extra shade and access to water will give you shelter if it gets too hot.
If you have a choice between hiking in the valley or in local mountains, spend the day hiking the mountains. 4,000 feet up will be noticeably cooler than down on the valley floor.
Include some salty snacks and at least 4 liters of water for the trail.
Take more frequent breaks and ensure that everyone is drinking water.
Be extra vigilant about blisters. The heat and extra sweating may help you experience your first blister in a long time so notice and treat hot spots
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