If you're sure that that's your temp (ie you're confident in your thermometer and its been well stirred and mixed), then you'll definitely want to bring that up. I think you'll still get some conversion at that temp, but it will lead to a very fermentable wort. Its possible that it might still taste fine, but its also easy to boil some water and add it to bring it up a little bit. You can also consider doing a two-step mash, where the second step is higher than your original mash (ie 156) to generate some more complex sugars. That way if it takes half an hour to get your water boiling, you're still ok with the mash.