The higher SPF formulas (above SPF30) will hold in your body heat which can be helpful in cold weather, but please be careful in warmer weather to make sure you can adequate cool yourself.
Intense sun conditions include:
- Low latitudes (near the equator)
- Higher altitudes
- Peak sun season: May, June and July in the Northern Hemisphere
- Intense time of the day 10am to 2pm
- Sun exposure after long periods with little sun exposure
On hot and humid days it is important to consider the need for your body to sweat and cool itself. Higher SPF formulas (and non breathable Matrix formulas) may inhibit heat transfer. It is important to remember this with younger children as they have not fully developed their ability to sweat. In such cases the lower SPF formula should actually provide better protection.
In special situations where you cannot apply the initial application of the sunscreen to cool and dry skin you may choose Sawyer's SPF 50 which is formulated to stick to moist skin (which is why it feels greasy) but you should take care and try to keep yourself as cool as possible. Areas of thin skin may need reapplications of the SPF 30 or even the special SPF 50 later in the day or after heaving rubbing or moisture exposure.