Oh lord, that's pretty much the exact opposite of cold storage. Don't use Blockchain if you're planning on running cold storage. To give you it simply:

1. Get a separate computer that is air gapped (Raspberry Pi's are good for this)
2. Install Electrum on your choice of Linux distro on your Pi
3. Get the Master Public Key from Electrum and copy it onto your main computer so you can view the balance without risking it getting stolen.
4. Create transactions on your comp connected to the net
5. Copy this tx to your offline Pi
6. Sign the tx with your offline Electrum
7. Bring it back to your main comp and broadcast.