I thought I would be extra clever as I knew it was going to be what we British call a "scorcher" here in London (29 degrees forecast) - so I put my water bottle in the freezer overnight. I cleverly didn't fill it up all the way, as any fool knows that water expands and didn't want my water bottle to explode.
I took it out before the school run, thinking by the time I started my "commute proper" it would be nice and melted.
A dry journey
I hadn't done my calculations properly. The ice remained stubbornly solid in the bottle throughout my commute of nearly an hour. As a result, instead of beautiful cool water, I got ... nothing. Until I limped through the office doors.
Clearly there's a moral. I think probably about two hours of freezing might be optimal. Or take it out of the freezer first thing. Or - radical thought - perhaps just put some ice cubes in it! Any other "keeping cool" tips out there?