diff --git a/lib/parse-args.js b/lib/parse-args.js
index 54be3c89..e0d0ffda 100644
--- a/lib/parse-args.js
+++ b/lib/parse-args.js
@@ -62,7 +62,8 @@ function buildYargs (withCommands = false) {
       type: 'boolean'
     })
     .option('temp-directory', {
-      describe: 'directory V8 coverage data is written to and read from'
+      describe: 'directory V8 coverage data is written to and read from',
+      default: process.env.NODE_V8_COVERAGE
     })
     .option('resolve', {
       default: '',
diff --git a/package.json b/package.json
index 18fb20be..43e067da 100644
--- a/package.json
+++ b/package.json
@@ -9,7 +9,7 @@
     "url": "git@github.com:bcoe/c8.git"
   },
   "scripts": {
-    "test": "node ./bin/c8.js --reporter=html --reporter=text mocha --timeout=4000 ./test/*.js",
+    "test": "node ./bin/c8.js --reporter=html --reporter=text mocha --timeout=8000 ./test/*.js",
     "test:snap": "CHAI_JEST_SNAPSHOT_UPDATE_ALL=true npm test",
     "posttest": "standard",
     "coverage": "./bin/c8.js report --reporter=html --reporter=text-lcov | coveralls",
diff --git a/test/integration.js b/test/integration.js
index b2753012..7bdc3f58 100644
--- a/test/integration.js
+++ b/test/integration.js
@@ -1,6 +1,7 @@
 /* global describe, before, beforeEach, it */
 
 const { spawnSync } = require('child_process')
+const { statSync } = require('fs')
 const c8Path = require.resolve('../bin/c8')
 const nodePath = process.execPath
 const chaiJestSnapshot = require('chai-jest-snapshot')
@@ -26,6 +27,23 @@ describe('c8', () => {
     output.toString('utf8').should.matchSnapshot()
   })
 
+  it('supports exeternally set NODE_V8_COVERAGE', () => {
+    const { output } = spawnSync(nodePath, [
+      c8Path,
+      '--exclude="test/*.js"',
+      '--clean=false',
+      nodePath,
+      require.resolve('./fixtures/normal')
+    ], {
+      env: {
+        'NODE_V8_COVERAGE': 'tmp/override'
+      }
+    })
+    const stats = statSync('tmp/override')
+    stats.isDirectory().should.equal(true)
+    output.toString('utf8').should.matchSnapshot()
+  })
+
   it('merges reports from subprocesses together', () => {
     const { output } = spawnSync(nodePath, [
       c8Path,
diff --git a/test/integration.js.snap b/test/integration.js.snap
index 0983a0b7..1c45ccbd 100644
--- a/test/integration.js.snap
+++ b/test/integration.js.snap
@@ -200,3 +200,22 @@ All files   |    70.37 |    66.67 |       60 |    70.37 |                   |
 ------------|----------|----------|----------|----------|-------------------|
 ,"
 `;
+
+exports[`c8 supports exeternally set NODE_V8_COVERAGE 1`] = `
+",hey
+i am a line of code
+what
+hey
+what
+hey
+what
+hey
+-----------|----------|----------|----------|----------|-------------------|
+File       |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
+-----------|----------|----------|----------|----------|-------------------|
+All files  |    83.33 |    85.71 |       60 |    83.33 |                   |
+ async.js  |      100 |      100 |      100 |      100 |                   |
+ normal.js |       75 |    66.67 |    33.33 |       75 | 14,15,16,18,19,20 |
+-----------|----------|----------|----------|----------|-------------------|
+,"
+`;
diff --git a/test/parse-args.js b/test/parse-args.js
index 04f29194..e742a4d2 100644
--- a/test/parse-args.js
+++ b/test/parse-args.js
@@ -6,6 +6,8 @@ const {
   hideInstrumenterArgs
 } = require('../lib/parse-args')
 
+const { join } = require('path')
+
 describe('parse-args', () => {
   describe('hideInstrumenteeArgs', () => {
     it('hides arguments passed to instrumented app', () => {
@@ -21,6 +23,18 @@ describe('parse-args', () => {
       const argv = buildYargs().parse(hideInstrumenteeArgs())
       const instrumenteeArgs = hideInstrumenterArgs(argv)
       instrumenteeArgs.should.eql(['my-app', '--help'])
+      argv.tempDirectory.endsWith(join('coverage', 'tmp')).should.be.equal(true)
+    })
+  })
+
+  describe('with NODE_V8_COVERAGE already set', () => {
+    it('should not override it', () => {
+      const NODE_V8_COVERAGE = process.env.NODE_V8_COVERAGE
+      process.env.NODE_V8_COVERAGE = './coverage/tmp_'
+      process.argv = ['node', 'c8', '--foo=99', 'my-app', '--help']
+      const argv = buildYargs().parse(hideInstrumenteeArgs())
+      argv.tempDirectory.endsWith('/coverage/tmp_').should.be.equal(true)
+      process.env.NODE_V8_COVERAGE = NODE_V8_COVERAGE
     })
   })
 })